The aim of this study is to compare the employment relationship of temporary agency and permanent workers in two different sectors analyzing the relationship between human resource practices systems and workers’ affective commitment and the mediating role of work engagement. The hypotheses were tested with multiple group analysis on two samples: from a call center and from two industrial companies. Results confirm that in both the temporary agency and the permanent subsamples in the two sectors workers’ perception of the human resource practices system relates positively with affective commitment toward the organization, and work engagement partially mediates this relationship. Moreover, the study confirms that the relationship between workers’ perception of the human resource practices system and affective commitment was stronger for temporary agency than for permanent workers. However, this moderation occurred only in the manufacturing sector. Contrarily, the relationship between workers’ perception of the human resource practices system and engagement was stronger for permanent workers than for temporary agency workers (TAWs) in this sector and the relationship between this psychological state and affective commitment was also stronger for permanent than for TAWs, in both sectors (call center and manufacturing).