The company began an aggressive expansion campaign near the end of the 1990s and moved its headquarters to Boston's Financial District.

[5] In 1997, Eastern began an aggressive expansion program with the aim of doubling its size within five years.

[7] The first acquisition of the program was initiated in early 1998 when Eastern bought the ten-branch Quincy-based Hibernia Savings Bank and its parent holding company Emerald Isle Bancorp, Inc for $80 million and converted all branches to Eastern Banks.

Eastern Bank announced in March 2008 its intention to buy Reading-based MassBank Corp. for $170 million.

The bank, "known for its social activism and lending to nonprofit organizations", was purchased for $163 million or $19 a share; almost double its $9.62 closing stock price prior to the announcement.

[12] In March 2014, Eastern signed a definitive agreement to acquire Bedford, N.H.-based Centrix Bank & Trust.