Communication with one's social network can take place in-person or using technology. Past studies have mainly focused on the effects of communication modality (in-person, telephone calling, text messaging, and internet) on stress and affect at a between-person level by exploring the individual differences. Yet few studies have compared such effects at a within-person level, that is, how an individual varies over time. We conducted a diary study over seven days for 145 participants (ages 22 to 94) mostly from the greater Boston area to test the role each communication mode played in daily stress exposure, stress reactivity, and positive and negative affect using within-person analyses. Multilevel modeling results revealed that days with more frequent text messaging were associated with greater stress exposure and negative affect. Days with more in-person communication were associated with more positive affect. Days with more telephone calls were associated with less negative affect. Internet communication was not associated with stress or affect at a within-person level. To address the directionality of our findings, we also conducted lagged analyses that suggested higher previous day frequency of text messaging was related to higher stress exposure on the subsequent day. In addition, higher previous stress exposure was related to less telephone calling on the subsequent day. Implications and future research are discussed with a focus on how social interactions via different communication modes with one's social network can make a difference for daily well-being.