Nichola Mallon was born in Belfast in 1979. She attended St Dominic's Grammar School and completed graduated with a BA in Economics and Politics from Trinity College Dublin, and an MA in Comparative Ethnic Conflict from Queen's University Belfast. She has worked in the Northern Ireland Civil Service and as a special advisor to the Northern Ireland Assembly Environment Minister.

In 2010, Mallon was co-opted on to Belfast City Council, representing the Social Democratic and Labour Party (SDLP). Mallon was elected to Council in 2011. She is the first female Irish nationalist politician to serve as Lord Mayor of Belfast.

Mallon was elected to the Northern Ireland Assembly in 2016. She chairs the Assembly's All Party Group on Housing. Mallon is the SDLP Communities Spokesperson.