Research on interpersonal behaviour is becoming increasingly important in a variety of social contexts and cultures. In educational practice, its importance is based on interactions as the educational context, in which learning, value formation and meaningful activities take place. The aim of this was to adapt the Interpersonal Behaviours Questionnaire (IBQ) in Sport into Lithuanian and to analyse its reliability and validity. 241 physically active men (mean age 27.01 ± 7.67) participated in this study. The adapted questionnaire showed good reliability (Cronbach [alpha] 0.927), content, criterion and structural validity (CFI 0.928, TLI 0.917, RMSEA 0.070, X[superscript 2]/df 2.21) of Lithuanian version of IBQ in sport. The structural validity of the scale showed that supportive behaviours are strongly related to autonomy, competence and relatedness needs (rs ranged from 0.843 to 0.877), while supportive and thwarting behaviours have a moderate inverse relationship. However, supportive and thwarting behaviours are not diametrically opposed (r = -0.597). Thus, the study shows that the IBQ in sport is valuable for analysing interpersonal relationships explaining the links between supportive and thwarting behaviour. The IBQ in sport can be a valuable tool for advancing research, enriching and improving educational practice in this field.