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This study aimed to investigate whether the presence of European minnow (Phoxinus phoxinus) affects zooplankton community structure and whether this could indirectly influence the biomass of brown trout (Salmo trutta) in mountain lakes. Zooplankton samples were collected from six subarctic lakes near Lake Torneträsk in northern Sweden, three of which contained both trout and minnows, and three of which contained only trout. Species were identified to genus or family level, body length was measured, and biomass was calculated to compare zooplankton size structure and abundance as well as biomass between lake types. Statistical analyses were performed in R using t-tests, Wilcoxon tests, and linear regressions to examine relationships between zooplankton biomass and fish biomass. A majority of the results do not indicate a difference in zooplankton biomass, size, or composition between lakes with and without minnows. No significant differences were detected in trout biomass with or without minnows, indicating little if any impact on trout by minnow, especially via competition for zooplankton. The statistical strength in this study is weak so further studies with larger sample sizes (lakes) and seasonal replication are needed to confirm these results.