This study explores Tibetan students' L2 and L3 motivational systems and their interactions based on the framework of the L2 Motivational Self-System proposed by Dörnyei. Five hundred fifty-two participants were invited to respond to a questionnaire regarding their Chinese (L2) and English (L3) motivational selves, learning experiences and intended learning efforts. Multiple regression analyses revealed that L2 motivational selves and L2 learning experiences could explain 55% variance of L2 intended learning efforts (ILEs); L3 motivational selves and L3 learning experiences can explain 57% variance of L3 ILEs. Positive as well as negative interferences were also found between their L2 and L3 motivational systems. Positive interferences were found between L2 and L3 ILEs, while L3 ought-to self exerted a negative effect on L2 ILEs; L2 positive learning experiences exerted a negative impact on L3 ILEs. But the positive interferences outweighed the negative ones. The findings hold multiple implications for CSL and EFL education in Tibetan areas.