Much research has identified safety motivation as an essential individuallevel antecedent of safety performance. Recently, scholars have shown interest in workplace support as an essential factor of safety motivation. While support from different sources is theoretically distinct, each is argued to be not just an antecedent, but also an outcome of the other. A similar reciprocal relationship is also expected between support and safety motivation. Our research utilised the Self-Determination Theory (Deci & Ryan, 1985) and Social Cognitive Theory (Bandura, 1988) to examine the role of each source of support on safety motivation; and investigate their reciprocal relationships. We used structural equation modelling to analyse three-wave longitudinal data (three months apart) from 314 firefighters throughout Malaysia. The result confirmed direct relationships and interestingly, denied that reciprocal relationships exist between organisational support, social support, and safety motivation over time. Our study recommends that the fire department should encourage support from all sources, primarily from senior management since it is the catalyst that activates support from other sources.