Although public service organisations have increasingly relied on nonstandard employees, little research has investigated their work experiences and job attitudes. This paper examines the mechanism by which temporary agency workers' experience of relative deprivation affects their organisational attachment toward their client firm in the public sector. Based on data collected from temporary help agencies working with an international airport in Korea, we found that the perceived likelihood of standard employment mediated the negative relationship of relative deprivation to organisational attachment. Moreover, the indirect relationship of relative deprivation with organisational attachment via perceived likelihood of standard employment was strong and significant among those with high public service motivation but was not significant for those with low public service motivation. We discuss the implications of this study in building a better understanding of relative deprivation and nonstandard work arrangements in the public sector.