National Socialism gained influence in Wiesbaden after Theodor Habicht reorganized the local branch of the NSDAP, which had been founded in 1926. In the elections to the city council in Jan. 1927, the party achieved just over 700 votes, but did not win a seat as a deputy. At the next ballot, which was necessary in May 1928 due to the incorporation of the city, over 6,000 people voted for the NSDAP, which gained four seats in the city parliament. Another election was held on November 17, 1929, with over 13,000 voters now voting for the party, which was now represented by nine city councillors in the town hall. In the Reichstag elections of 1930 and 1932, the results in Wiesbaden NSDAP were well above the national average.

The effects of the global economic crisis since 1929, the years of occupation with two separatist coup attempts, but especially the end of the spa town in the traditional sense, which was sealed in 1918, and the resulting dramatic slump in municipal revenues contributed significantly to the success of National Socialism in Wiesbaden. The number of unemployed rose from 8,000 in 1928 to 20,000 in February 1933; of the approximately 150,000 Wiesbaden citizens, one in three lived on welfare benefits. The city's financial situation was so hopeless that a compulsory budget was set in 1930 and 1931.

It was only logical that the end of the Franco-English occupation in June 1930 and the visit of Reich President Hindenburg three weeks later caused a national frenzy of enthusiasm, which was skillfully exploited by the Nazis. However, there had already been bloody clashes between political opponents beforehand. The violent riots were further fueled by the Nazi press organs, such as the "Nassauer Beobachter", published by Habicht since the beginning of July 1927, and its successors, the daily newspaper "Rheinwacht" and the "Nassauer Volksblatt" (until 1943). The sale of the "Wiesbadener Zeitung" to the "Nassauer Volksblatt" in 1936 contributed significantly to the fact that other political opinions could no longer be expressed and the press landscape was further standardized. Visits by leading Nazi officials throughout the Reich served to agitate the population: Robert Ley stayed in Wiesbaden in 1926 and 1928. Fritz Sauckel, Julius Streicher, Heinrich Himmler and Joseph Goebbels were repeatedly in Wiesbaden between 1928 and 1932. High-ranking Nazi representatives came to Wiesbaden, especially in the run-up to the five elections in 1932: Prince August Wilhelm of Prussia appeared at the Paulinenschlösschen in March; on April 3, Goebbels gave several speeches in Wiesbaden.

Hitler stopped off in Wiesbaden in April on one of his "Germany flights". He visited the city again on 28.07.1932 in the run-up to the Reichstag elections three days later. On 30.01.1933, the day of his appointment as Reich Chancellor, there were protests by the workers' parties and trade unions, and on the evening of 31.01.1933 there were violent clashes with political opponents and several arrests during a "Hitler homage march" with a torchlight procession. The last election campaign of the Nazi opponents was massively obstructed, their supporters and representatives were harassed and imprisoned, their facilities searched and often demolished. Despite this, 17.7% of Wiesbaden voters still voted for the SPD, 12% for the KPD and just under 10% for the Center Party in the Reichstag elections on 5 March 1933. The NSDAP accounted for 46.2 % (Reich average 43.9 %). On March 8, 1933, the swastika flag was hoisted above the town hall. In the local elections four days later, 48.5% voted for the NSDAP in Wiesbaden. Lord Mayor Georg Krücke was arrested and replaced by Alfred Schulte, who was succeeded on 01.04.1937 by Erich Mix and later (temporarily) by Felix Piékarski. On March 31, 1933, the city parliament decided, against the votes of the SPD and Ferdinand Grün of the Centre Party, to make Hitler an honorary citizen of the city and to rename Schlossplatz Adolf-Hitler-Platz.

The representatives of the KPD had already been expelled from the town council immediately after the local elections on March 12; the Social Democrats met the same fate a little later. On May 2, 1933, the SA stormed and vandalized the trade union building in Wellritzstraße. In the period that followed, the bourgeois parties were forced to dissolve themselves, while the SPD and its subsidiary organizations were banned from operating on 22 June. The magistrate and city council were dissolved, and with the appointment of Gauleiter Jakob Sprenger as "Commissioner of the NSDAP", the Führer principle was enforced instead. The Wiesbaden councillors, who met for the first time on 27.09.1935, only had an advisory role. Political rallies and parades, e.g. on May Day or Thanksgiving Day, special SA and SS marches increasingly shaped the everyday life of the population. The town's budget situation gradually consolidated; the number of unemployed fell due to the resurgence of tourism and remilitarization.

Visible results of the upswing were the inauguration of the Opelbad in 1934 and the so-called brown fair in the Paulinenschlösschen, where local, "purely Aryan" crafts were presented (October 1933). The brown rulers also set new accents in cultural life, in particular through the local "Kampfbund für Deutsche Kultur". After Paul Bekker, Carl von Schirach, the father of the later Reich Youth Leader, took over the directorship of the state theater. The cultural needs of the inhabitants were met by events such as the parade for the fictitious 2000th anniversary of the town (1934), the organization of Gaukultur and music weeks, all kinds of lectures and summer festivals. The anti-Jewish and anti-socialist defamatory exhibition "Degenerate Art" with works of art from the Dresden Gallery was shown in the State Museum in March 1937. In addition, the military parades, marches and torchlight processions, with which all events of national importance were celebrated, became more frequent.

Hitler paid another visit to Wiesbaden from March 20-23, 1935. The following year, the abolition of the demilitarized zone on both sides of the Rhine on 7 March 1936 created the conditions for Wiesbaden's remilitarization. In October, the regimental staff and the III Battalion of the Infantry Regiment 38 moved to Wiesbaden, followed 14 days later by the General Command of the XII. Army Corps and an air district command moved into the town. The expansion of the city as a garrison was steadily advanced from October 1937 with the air base of the Luftwaffe in Erbenheim, the relocation of further military headquarters and the construction of new barracks.

Apart from the military facilities, Wiesbaden was also home to one of 30 Gau administrations of the Reich Labor Service and, since 1939, a "Lebensborn" home as well as several offices of the NSDAP, SA and SS. Above all, Wiesbaden was the location of the Higher SS and Police Leader Rhine-Westmark, who was responsible for military district XII and the planned Reichsgau Westmark, including Lorraine and Luxembourg, which was also occupied in 1940. The office was held by SS-Gruppenführer and Lieutenant General of the Police Jürgen Stroop from the end of 1943-45. The Wiesbaden branch of the Frankfurt/Main Gestapo, which was responsible for the deportation of Wiesbaden's Jews, was located in Paulinenstraße; Gestapo officer Walter Bodewig held the position of "Judenreferent". On April 1, 1933, the day of the nationwide boycott of Jewish stores, SA men positioned themselves in front of Jewish stores, daubed their shop windows with anti-Semitic slogans and tried to deter customers from shopping. The silk merchant Salomon Rosenstrauch at Wilhelmstraße 20 and the milk merchant and SPD cashier Max Kassel were the first Jewish murder victims in Wiesbaden (22.04.1933).

In the period that followed, the persecution of the Jews intensified. On November 10, 1938, the synagogues were attacked, demolished and in some cases set on fire, including the synagogue on Michelsberg. Around 1,500 Jews were murdered by the end of the war. Many functionaries of the workers' parties and trade unions were also persecuted, as were the Sinti and Roma living in Wiesbaden, the "Jehovah's Witnesses", homosexuals, physically or mentally disabled people and people in permanent need of help.

Despite the constant surveillance, harassment and various reprisals, numerous men and women - communists, social democrats, trade unionists, bourgeois opponents of the Nazis - also offered resistance in Wiesbaden. With the outbreak of the Second World War, the majority of men in Wiesbaden were called up for military service. The result was a blatant labor shortage, which was attempted to be compensated for by the increased use of forced laborers and prisoners of war. With the American invasion on March 28, 1945, National Socialism came to an end in Wiesbaden. There was no resistance worth mentioning to the occupiers, Mayor Piékarski and other Nazi officials had fled, the Wehrmacht, SS and police units had withdrawn.