Abstract: Brook trout (Salvelinus fontinalis) face many threats throughout their native range in the eastern United States including climate change, invasive species, and recreational angling. Understanding the habitat requirements and distribution of young of the year and adult brook trout in small headwater streams is essential for the conservation of the species. With this research, we sought to better understand the distribution pattern of young of the year, detect seasonal movement of adults before and during the spawning season, and determine if young of the year and adults preferentially inhabit stream reaches of different sizes. To explore these fish-habitat relationships, we electrofished 30 meter reaches with catchment areas ranging from 0.09 km2 to 4.90 km2 in the headwater systems of two western Massachusetts watersheds. Sampling was conducted during the spring and fall of 2014. We used generalized linear mixed models to evaluate young of the year density and linear density, adult density and linear density, and mean length of all fish sampled. The results for young of the year indicate that their distribution is quadratic or increases with stream size. We found no seasonal differences in adult densities. We also did not find a longitudinal difference in mean length. These results lead us to believe that the catchment sizes included in this study are equally important for brook trout persistence and should all be considered conservation priorities. This study demonstrated a need for additional research in the upper reaches of headwater streams since our models did not explain a significant proportion of the variability in the data. Additional landscape variables should be measured to better understand how brook trout population dynamics vary longitudinally in headwater streams and how the streams should be managed in the future.