This paper describes effects of nanoparticle composition on energy transfer and ratiometric fluorescent response to singlet oxygen (1O2) of a series of acene-doped conjugated polymer nanoparticles (CPNs). These CPNs are comprised of the conjugated polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-(2,1’,3)-thiadiazole) (F8BT) as polymer donor matrix and one of four different 1O2-sensitive acene acceptor dopants. In the dense chromophore matrix of the CPN, the quantum yield of fluorescence of each acene-doped CPN matches or exceeds that of the undoped F8BT CPN. Reactivity with 1O2 of the acenes follows the same trend in the solid matrix of CPNs as previously found in dilute solution. The doping levels of acenes in the CP matrix have important implications for both the extent of energy transfer and the subsequent rates of ratiometric response. This study therefore lends important insight into the rational design of luminescent, stimuli-responsive CPNs and the reactivity of singlet oxygen in heterogeneous material systems.