The win surpassed the team's previous record of 50, set in 2014-15.
Though the Islanders are well out of the playoff picture, the victory was no smooth sailing.
The Bolts held leads of 4-1 and 7-3 in the contest, but after a late surge from the Islanders, they were forced to hang on to a 7-6 win.
In the process, Jon Cooper surpassed John Tortorella for the most head coaching wins in team history, per Bryan Burns of the team's website.
The Lightning now sit at 106 points - six ahead of the Boston Bruins for first place in the Atlantic Division and the Eastern Conference.