In this study, based on the approach of humanization of the postmodern organizations and depending on the conceptual background, it was suggested that psychological capital and social capital could be the significant antecedents of employee happiness at workplace. Further, it was proposed that organizational trust has a moderating role on the impact of psychological capital on happiness at workplace. Thereby, a cross-sectional research study has been performed in Turkey with the participation of 222 employees from a variety of sectors including sales, marketing, health, banking, finance and education. According to the findings, it was reported that the psychological capital construct (beta=,778; t=18,370, p<,05) and social capital (beta=,746; t=16,621, p<,05) had significant positive impacts on employees' happiness at workplace. These findings supported the proposed hypothesis 1 and hypothesis 2. In addition, it was demonstrated that organizational trust has significant positive impact on happiness at workplace (beta=,544, t=9,590, p<,05). However, the results indicated that organizational trust has no significant moderating role (p>0,05), thus hypothesis 3 was not confirmed. Further research direction and the need for research on organizational trust's moderating role are discussed. The conceptual and practical implications of the study are provided along with the concluding remarks and discussions.