The 1981 NBL season was the third season of the National Basketball League (NBL).

The regular season took place over 18 rounds between 14 February 1981 and 21 June 1981. Each team played 22 games, against every opponent twice.

Updated to match(es) played on 21 June 1981. Source: NBL.com.au

The NBL tie-breaker system as outlined in the NBL Rules and Regulations states that in the case of an identical win–loss record, the results in games played between the teams will determine order of seeding.

¹St. Kilda Saints chose to participate in the 1981 FIBA Club World Cup in Brazil, instead of the 1981 NBL Finals. They were replaced by the Brisbane Bullets.

²4-way Head-to-Head between West Adelaide Bearcats (5-1), Nunawading Spectres (3-3), Brisbane Bullets (2-4) and Newcastle Falcons (2-4).

³Head-to-Head between Brisbane Bullets and Newcastle Falcons (1-1). Brisbane Bullets won For and Against (+15).

⁴Head-to-Head between Coburg Giants and Bankstown Bruins (1-1). Coburg Giants won For and Against (+24).

The NBL finals series in 1981 consisted of two semifinal games, and one championship-deciding grand final. All three of these finals games were sudden death.