Monserrate contested his first election in 2002 on a United Goans Democratic Party ticket from the TaleigaoVidhan Sabha constituency. His opponent was two-term sitting member of the Assembly Somnath Datta Zuwarkar from the Indian national congress. Monserrate defeated Zuwarkar by about two thousand votes and was elected for the very first time to the Goa assembly. Monserrate was made a Minister of Town and Country Planning in the Manohar Parrikar led Government. In 2005, Monserrate and two other ministers resigned from the Manohar Parrikar led Government leaving it in a minority and thus bringing down the Bharatiya Janata Party Government of Goa. In the coming by-election, Monserrate switched sides and fought the election on an Indian national congress ticket and won the election by defeating Silveira Agnelo Mariano of the Bharatiya Janata Party by about four thousand votes. Monserrate was made a minister in the congress government under Chief MinisterPratapsingh Rane. In the 2007 assembly elections, Monserrate was pitted against Silveira Agnelo Marian of the Bharatiya Janata Party. Monserrate won that election by about two thousand votes and was appointed the Education minister of the state under Chief Minister Digambar Kamat. In the 2012, assembly election Monserrate vacated his safe seat of Taleigao for his wife Jennifer Monserrate and contested from the Santa Cruz constituency. Monserrate won that election on a Congress ticket defeating Rodolfo Louis Fernandes by about two thousand three hundred votes. In that same election, Monserrate's wife Jennifer Monserrate also won her election from the Taleigao Vidhan Sabha constituency thus making history of sorts by having a wife and husband to be elected to the Goa Assembly. He was expelled from the Indian National Congress in 2015 for six years for "anti-party activities". Monserrate contested the 2017 election from the Panaji and lost to Sidharth Sripad Kuncalienker of the Bharatiya Janata Party by about a thousand votes. In July 2017 Monserrate joined the Goa Forward Party.
Rape Allegations
In May 2016, Goa police arrested Monserrate for rape of a minor.
