By the mid-1880s, Moszkowski was suffering from nerves and began to curtail his recital activity in favor of composing, conducting and teaching. His many published compositions proved very popular in the era of salon pianism, and netted the composer a handsome income. These included the Serenata Op. 15/1, Concert Studies Op. 24, Caprice Espagnol Op. 37, Etincelles Op. 36/6 and Guitarre Op. 45/2. Moszkowski's music for piano duet was especially popular, in particular the Spanish Dances Opp. 12, 21, and 65. Early in his career Moszkowski had some success with orchestral music as well, but these pieces remained largely unpublished and most are now lost.
Among Moszkowski's honors were membership in the Berlin Academy of Art, and an honorary lifetime membership in the Philharmonic Society in Britain, where he often appeared as conductor. Upon leaving the Neue Akademie der Tonkunst, Moszkowski re-settled in Paris with his wife, the sister of the composer Cecile Chaminade. In 1910 Moszkowski's wife left him for his best friend, taking their daughter with her; he never truly recovered from this personal tragedy. In the early years of the twentieth century Moszkowski proved unable to adapt to changing musical styles, and sales of his works quickly declined. Having lost his considerable fortune during the tumult of the First World War, Moszkowski was living in poverty by the early 1920s. On December 21, 1921 a group of concerned colleagues arranged a benefit concert at Carnegie Hall on his behalf; among the 14 pianists who played the event were Percy Grainger, Harold Bauer, Wilhelm Bachaus, Leo Ornstein, and Ignaz Freidman. The conductor of this "monster concert" was Walter Damrosch, who remembered that this event as the most difficult assignment of his career. Nonetheless, the concert generated $10,000; however Moszkowski was unable to access this windfall of cash until mere weeks before his death in Paris at age 70. Despite living up to the very eve of electrical recording, Moszkowski is not known to have left behind any records or piano rolls of his own playing.