The 2015 NBL season was the 34th season of the National Basketball League. The season draw was supposed to be released in December 2014, but the withdrawal of Otago and Waikato prompted a rethink for the 2015 competition format. In the past, each team played each other twice in a 10-team competition, meaning each franchise had nine home games. However, with two fewer teams in 2015, it was decided the new format would be played over two and half rounds to keep incomes at a similar rate for the remaining sides. Each team was scheduled to play each other twice and play three of the sides in a third game.^[1][2]

The 2015 pre-season tournament was held at the Te Rauparaha Arena in Porirua on Saturday 21 March and Sunday 22 March.^[3][4] The Wellington Saints were the only team to go undefeated over the two days, finishing with a 3–0 record.^[5] The regular season commenced on Wednesday 1 April in Invercargill with the Southland Sharks hosting the Manawatu Jets at Stadium Southland.^[6]

In the regular-season finale on Sunday 28 June, Taranaki Mountainairs import Aaron Fuller set the National Basketball League record for points scored in a game. With 54 points, Fuller broke John Whorton's record of 50 points, which was set in 2003.^[7][8] Despite Fuller's 54 points and 19 rebounds, the Mountainairs lost to the Super City Rangers to finish the season with a winless record (0–18). The 2015 Mountainairs side joined the 1998 Northland Suns, 2009 Mountainairs and 2010 Otago Nuggets as the only sides in NBL history to go an entire season without a win.^[9]

The Final Four weekend was held in Wellington for the fourth time in five years, with the semifinals on Saturday 4 July, followed by the championship game on Sunday 5 July.^[10]