Spatial navigation relies on external cues, such as visual objects, to anchor internal representations of space. In rodents, moving a visual landmark results in a corresponding shift in the tuning of head direction (HD) cells1. However, little is known about where visual objects are encoded in the mouse brain2 or how visual objects modulate the firing properties of HD cells3. Using functional ultrasound (fUS) imaging4, we conducted a brain-wide screen to identify areas preferentially activated by visual objects compared to scrambled versions of the same stimuli. Our results showed that while visual areas did not exhibit a preference for objects, regions involved in spatial navigation–in particular the postsubiculum (PoSub), the primary cortical area of the HD system–were more responsive to object stimuli. We next examined how visual objects impacted spatial coding in PoSub. To obtain HD tuning information, we implanted an electrode and recorded from PoSub neurons as mice freely moved around an open field arena with one wall-mounted visual landmark. Immediately afterward, mice were head-fixed to record visual responses to object and scramble stimuli. This revealed a preference for objects in both HD cells and fast-spiking interneurons. Lastly, we considered how visual objects impacted HD population coding. HD cells are organized as a continuous ring attractor. In head-fixed conditions, we found that visual stimuli modulated HD cell activity, increasing firing rates for HD cells aligned toward the visual stimulus, and suppressing activity for HD cells coding other directions. In the open field arena, by comparing similar HDs but when the animal was either looking at or away from the visual landmark, we found the same effect. Thus, visual objects dynamically refine population-level HD coding. These results reveal an interaction between visual object processing and the brain’s spatial navigation system that may help anchor internal spatial representations.