COVID‐19 disrupted infant contact with people beyond the immediate family. Because grandparents faced higher COVID‐19 risks due to age, many used video chat instead of interacting with their infant grandchildren in person. We conducted a semi‐naturalistic, longitudinal study with 48 families, each of whom submitted a series of video chats and surveys, and most (n = 40) also submitted a video of an in‐person interaction. Families were mostly highly‐educated, White/Caucasian, and lived between 1 and 2700 miles apart. We used multilevel models to examine grandparents’ and parents’ sensitivity during video chat across time (centered at February 1, 2021, the approximate date of vaccine availability). Grandparent video chat sensitivity changed as a function of date and parent sensitivity. Parent sensitivity changed as a function of date, grandparent sensitivity, and geographic distance. We then modeled infants' affective valence during video chat and in‐person interactions with their grandparents, which was only predicted by grandparent sensitivity, not modality or other factors. This study demonstrates that caregivers were sensitive toward infants during video chat interactions despite fluctuations in family stress and reduced in‐person contact during COVID‐19 and that grandparent sensitivity predicted positive infant affect during both video chat and in‐person interactions.