In 1866 Lechner went to Berlin, where he spent three years at the Academy of Architecture with Alajos Hauszmann and Gyula Pártos, studying under Karl Bötticher, who became a great influence with his lectures on building materials, especially the role of iron-framed structures.

In 1869 he went into a partnership with Gyula Pártos and the architecture firm received a steady flow of commissions during the boom years of the 1870s, during the construction of buildings lining the ring roads on the Pest side of the Danube.

The commissions the partners received were primarily apartment houses in which Lechner worked in the prevailing historicist style, drawing on neo-classical influences from Berlin and the Italian Renaissance.

The building's glazed tiles, the pyrogranite decorative elements, and the pierced floral motifs testify to Lechner's newfound Indian, Persian, Moorish, and Hungarian folk influences, as well as the cladding theories of German architectural theorist Gottfried Semper.

These developments in his vocabulary arguably reached their peak with the new Royal Postal Savings Bank (today the Hungarian State Treasury), on Hold utca in Budapest, built from 1899 to 1904.

On 1 July 1900 he was named a "Királyi tanácsos" (Royal Counselor) to the King of Hungary, Emperor Franz Josef I, and for his work on the building the Hungarian Képzőművészek egyesülete (Association of Fine Artists) awarded him their "Nagy Aranyéremmel," or Grand Gold Medal.

In the early 1900s, he received some small assignments, such as the reconstruction of the Dominican House in Szeged; the entrance to the Ernst Museum, Budapest; the Balázs Sipeki Villa; and the Péter Vajda Street School; but he enjoyed little success in his search for larger commissions.