Several Synalpheus species have been reported as hosts of bopyrid parasites; however, the impact of infestation on egg production is still unknown. Therefore, the present work studied reproductive aspects and the effect of parasitism on fecundity of the alpheid shrimp Synalpheus yano from Bocas del Toro, Caribbean coast of Panama. Un-infested females (N = 84) ranging from 3.7 to 9.6 mm carapace length, produced between 5 and 246 eggs (average: 98±64.6), and egg number increased significantly with female size. The eggs were relatively large (0.6–1.3 mm in diameter), but within the range of other Synalpheus species, and egg size did not differ significantly between un-infested and infested females. Despite these large eggs, the morphological characteristics of hatching larvae indicate a planktotrophic development. During the incubation period, the egg volume increased from 0.100 to 0.218 mm3, representing an overall increase of 118%. A total of 18 females (16% of all ovigerous individuals) were infested, and the occurrence of parasitic infestation was more pronounced in larger females. Infested females ranging from 4.6 to 9.4 mm carapace length, produced between 22 and 166 eggs (average: 81±44.4). Egg-bearing females infested by parasitic bopyrids carried on average 41% fewer eggs than similar-sized females without parasites. The co-occurrence of parasites and developing eggs, however, indicates that the bopyrid parasite does not necessarily castrate its host. Therefore, we encourage more comparative intraspecific studies on egg production in infested and un-infested females to assess the impact of infestation on fecundity in caridean shrimp.