In 2000, at the age of 12, Masami Nagasawa won the top prize in the fifth "Toho Cinderella" selection competition. In the same year, she entered the entertainment industry with the suspense film "Going Crazy".

In 2002, she starred in the fantasy romance film "Return from the Netherworld".

In 2003, she won the Newcomer Award at the 27th Japan Academy Awards for her role in the comedy film "Robot Contest".

In 2004, she won the Best Supporting Actress Award at the 28th Japan Academy Awards for her role in the pure love film "Call for Love in the Center of the World".

In 2006, she was nominated for Best Actress at the 30th Japan Academy Awards for her role in the pure love film "Tears Shining".

In 2007, she starred in the pure love drama "Proposal Battle".

In 2008, she starred in the social ethics drama "The Last Friend".

In 2009, she starred in the Taiga drama "Heaven, Earth and Man".

In 2010, she starred in the TV series "GOLD".

In 2011, she won the Best Supporting Actress Award at the 54th Blue Ribbon Awards for her role in the romantic comedy film "The Peach Blossom Season".

In 2012, she won the Best Leading Actress Award at the 73rd Nikkan Drama Academy Awards for her role in the detective drama "The Legend of the City".

In 2013, she starred in the detective drama "Urban Legend of the Daughter Season 2".

In 2014, he starred in the disaster romance film "Taiping Ship (Part 1)".

In 2015, she won the Best Supporting Actress Award at the 70th Mainichi Film Awards for her role in the drama film "Diary of the Sea Street".

In 2016, she starred in the Taiga drama "Sanada Maru".

In 2017, she was nominated for Best Actress at the 41st Japan Academy Awards for her role in "The Walking Invaders".

In 2018, she won the Best Actress Award at the 97th Nikkan Television Drama Academy Awards for her role in the suspense comedy "The World of Deception JP".

In 2021, Masami Nagasawa won the Best Actress Award at the 44th Japan Academy Awards for her role in "Mother".

On March 24, 2023, the film "Death Nurse" in which she starred was released.

On May 18, 2024, the film "April Girlfriend" in which she starred was released in China.