Taking absorptive capacity effects on research spillovers into consideration, this paper focuses on the R&D investment decisions and the output decisions of labor-managed firms. Based on the general model of the cost-reducing R&D, the strategic interactions of output and R&D investment between labor-managed firms in a duopoly are analyzed. Moreover, the impact of absorptive capacity effects on optimal output in the production stage is discussed. In the R&D stage, the impacts of absorptive capacity effects on the equilibrium R&D investment in cooperative and non-cooperative R&D are analyzed. Finally, the R&D strategy of labor-managed firms is compared with the behavior of profit-maximizing firms. The results show that equilibrium R&D investment is always higher than that in the exogenous spillover rate, which is similar to the behavior of the profit-maximizing firms. However, unlike the profit-maximizing firms, the impact of the absorptive capacity that affects the relationship between the optimal output and its own(rival' s)R&D is shown to be dependent upon a return-to-scale of the production.