He co-founded the Partito dei Lavoratori Italiani in 1892 after renouncing his anarchist principles in 1879. It is probable that this happened due to his marriage to Russian Socialist Anna Kulischov. In his book My Years in Exile, Edward Bernstein wrote of the conversion: "When [ Filippo Marzotti ] first heard the news that Costa was lost to the Anarchist cause, he excitedly raised his hands above his head, and cried repeatedly, almost in desperation: 'Anna! Anna! Anna!'".
He died in Imola in 1910.
- G. Gamberini (Great Master of GOI) (1975). Mille volti di massoni. Rome: Erasmo. p. 175. LCCN 75535930. OCLC 3028931. Collana del Grande Oriente d'Italia , op. 3
- "The epitaph of Andrea Coosta (written by Giovanni Pascoli)". loggiagiordanobruno.com (in Italian). Retrieved Sep 23, 2018.
- V. Gnocchini (Sep 1, 2005). L'Italia dei Liberi Muratori. Milan, Rome: Mimesis-Erasmo. pp. 85–86. ISBN 9788884833624.
- "Biography of Andrea Costa". cronologia.leonardo.it (in Italian). Archived from the original on Sep 28, 2017. Retrieved Sep 23, 2018.
- R. Boschetti. "Giovanni Pascoli: portrait of a young socialist poet". storiain.net (in Italian). Archived from the original on Jun 21, 2017. Retrieved Sep 23, 2018.
- Centenario della morte di Andrea Costa Biography, photographys etc. (Italian website)
- Edward Bernstein: My Years of Exile (Chap.2) at www.marxists.org