Increasing marine microplastic pollution has detrimentally impacted organismal physiology and ecosystem functioning. While previous studies document negative effects of microplastics on coral reef animals, the potential responses of organisms such as large benthic foraminifera (LBF) are largely unknown. Here, we document the impact of microplastics on heterotrophic feeding behavior of LBF. Specimens of Amphistegina gibbosa were incubated in three experimental treatments: (1) Artemia sp. nauplii only; (2) pristine microplastic particles only; and (3) choice of nauplii and pristine microplastic. Feeding responses were evaluated 24 h after initiation of treatments. A separate experiment was conducted to compare the effect of conditioned vs. pristine microplastic. Our results indicate that A. gibbosa is able to selectively feed on Artemia, avoiding interactions with pristine microplastic. However, the presence of conditioned microplastic causes similar feeding interaction rates as with Artemia. This suggests that microplastics with longer residence times may have a larger impact on facultative detritivores.