The goal of the study was to determine the extent to which seafarers' work and life satisfaction can be explained by the six aspects of work motivation based on the Self-Determination Theory. The research was conducted on a convenience sample of Croatian seafarers (N = 286), ranging from 18 to 65 years. The applied questionnaire consisted of sociodemographic and work characteristics questions, and measures of job satisfaction, life satisfaction, and six dimensions of work motivation. The results of regression analyses showed that two dimensions of work motivation with the highest level of self-determination contribute positively to the explanation of job satisfaction and life satisfaction: intrinsic motivation and integrated regulation. Furthermore, external regulation contributes positively to the explanation of life satisfaction, while amotivation has proven to be a significant negative predictor of job satisfaction. The results indicate the importance of developing and encouraging autonomy in work motivation in seafarers, but also the specifics of work motivation that are associated with the socio-economic context of the maritime profession in Croatia.