On 16 February 2015, during the 2014–15 season he played in his 100th career NHL game in Tampa Bay's 3–2 loss to the Los Angeles Kings. On 30 March, the Lightning announced that Šustr would be out one-to-two weeks with an upper body injury, but was expected to return in time for the start of the 2015 playoffs. On 18 April, he scored his first career playoff goal in a 5–1 Lightning win over the visiting Detroit Red Wings.
On 30 June 2015, the Tampa Bay Lightning re-signed Sustr to a two-year, two-way contract. Sustr played in 72 games with the Lightning in the 2014-15 NHL season, recording 13 assists and 34 penalty minutes. Sustr set career highs in games played, assists, plus/minus (+10) and penalty minutes. Sustr also appeared in 26 Stanley Cup Playoff games for the Lightning, registering one goal and two points. Sustr has skated in 117 NHL games, all with the Lightning over the past three seasons, collecting one goal and 21 points. Sustr ranked fourth on the Lightning for blocked shots with 84 during the 2014–15 season. He also set the Lightning franchise record for the best plus/minus (+7) in a playoff series in the first round of the 2015 Stanley Cup playoffs against the Detroit Red Wings.