Leisure-time physical activity has a complex relationship with low back pain (LBP). Thus, we aimed to investigate whether the diversity of sport activities is associated with the type of LBP. In the FinnTwin16 study, 4246 (55% females) Finnish twins at mean age 34.1 years replied to a health behaviour survey in 2010-12. Based on participation in different sport activities, we created two measures of diversity: quantity (i.e., the number of sport activities: 1, 2, 3, 4, and ≥5) and quality (i.e., the type of sport activity: endurance, strength, body care, etc.). Based on the frequency, duration, and type of LBP, we created three groups: no history of LBP lasting more than one day, radiating LBP, and non-radiating LBP. The associations between the quantity and quality of sport activities and type of LBP were investigated with logistic regression analyses. Participation in ≥5 sport activities associated with less radiating and non-radiating LBP in analyses pooled across sex (odds ratio 0.46, 95% CI 0.30-0.69 and 0.66, 0.44-0.99, respectively). However, the associations attenuated after adjusting for several confounders. Participation in endurance sports was associated with less radiating (0.58, 0.43-0.76) and non-radiating (0.60, 0.44-0.81) LBP, whereas strength sports and body care only with less radiating LBP (0.76, 0.58-1.00 and 0.26, 0.09-0.74, respectively) adjusted for all sport types. On a sport-specific level, running and cycling were associated with less radiating and non-radiating LBP. In adulthood, the diversity of sport activities, particularly participation in endurance sports, may be associated with less radiating and non-radiating LBP.