Background/purpose: We developed an intervention based on transcontextual model (TCM) to promote autonomy supportive style in teaching sport safety in secondary school. We believed that would in turn facilitate students’ intention in adopting sport injury prevention behaviour in an out-of-school or unsupervised context following the TCM sequences. Methods: Three secondary schools, including 6 of their PE teachers and 1,199 of their students (Mage=13.33 ± 1.06, range=12 to 16; Male=48.57%) participated in a 3-month randomised control trial, which consisted of two waves of assessments (i.e., baseline and 3-month). The schools were randomly assigned into intervention group (whose PE teachers received a workshop and a smartphone phone application) and control group (whose PE teachers did not receive any material). Student participants completed a survey that measured the TCM variables during the time of assessments. Under the intent-to-treat principle, we conducted path analysis of the standardised residual changes scores of the TCM variables using Mplus. Results: The proposed TCM model displayed adequate fit to the data, χ2=145.87 (df=15), CFI=.95, TLI=.91, and RMSEA=.09 [90% CI=.07 to .09], and SRMR=.08. The intervention had positive and significant effects on perceived autonomy support (β=.09, p<.01), that in turn formed positive and significant direct (β=.09 to .64, p<.01) and indirect (β=.01 to .04, p<.01) effects with other motivational and social cognitive variables, and intention of sport injury prevention. Conclusions and implications: The TCM might be useful for promoting secondary school students’ intention in adopting sport injury prevention behaviours.