She starred in several Victor Herbert operettas and performed with her own Alice Nielsen Opera Company.

Outside the Kansas City Club, she was heard by wealthy meat packer Jakob Dold and invited to sing at his daughter's birthday party.

When the marriage turned violent she left for San Francisco on the vaudeville circuit, joined by Arthur Pryor, performing with Burton Stanley and Pyke Opera.

In the Spring of 1905, Nielsen returned[clarification needed] to London's Covent Garden to perform in several Mozart operas.

She joined the roster of the San Carlo Opera Company (SCOC), at that time a touring arm of the Teatro di San Carlo of Naples led by Henry Russell, the following fall for their guest Fall season in residence at Covent Garden with Enrico Caruso and Antonio Scotti.

[4] After the SCOC's Fall season in London ended, the company became its own separate entity under the direction of Russell, severing ties with the opera house in Naples and moving its base of operations to Boston.

In summer 1906, Nielsen joined Eleonora Duse and Emma Calvé in a joint program of related operas and dramas to open the Shuberts' Waldorf Theatre.

That fall, Nielsen toured America with the SCOC presenting opera concerts featuring a shortened version of Donizetti's Don Pasquale.

After a difficult debut in New York City, she became a hit by springtime in Chicago, San Francisco, Los Angeles, and Dallas.

In winter 1907, Nielsen returned to America with Lillian Nordica, Florencio Constantino and a full company for the SCOC's season at New Orleans' French Opera House.

At the end of the tour, in Boston's Park Theatre during March 1908, the SCOC presented a week of nightly grand opera performances featuring Nielsen and Constantino.

The renditions of La bohème and Faust at the Park Theatre created such a sensation that Boston's music patron Eben Jordan offered to build a new opera house for the SCOC's director Henry Russell and his company.

During the 1910s, Nielsen sang in joint concerts with John McCormack and other artists at Carnegie Hall and in national tours.

In later years, she owned a house in Far Rockaway, Queens, near her brother, who was the parish organist for St. Mary, Star of the Sea Church.