People living alone are often depicted as prone to social isolation and poor well-being. Since previous research largely focused on comparisons between the living arrangements of older adults, evidence on differences within middle-aged adults living alone remains sparse. The present study used a person-centered approach to allow for a comprehensive understanding of the heterogeneity of living alone in midlife. Middle-aged adults (N = 389; aged 35-60 years) reported on their personal networks, personality, and well-being and completed diaries on daily network interactions. Using latent class analysis, we constructed a network typology and examined differences in social motives, well-being, daily interaction quantity, and daily relationship quality. We found four structural network types: Individuals with diverse networks (highest in size, contact, proximity, and heterogeneity) felt less lonely than individuals with restricted (lowest in size, contact, proximity, and heterogeneity) or loose-knit networks (low in contact). Individuals with loose-knit networks reported poorer well-being than those in diverse or partner-focused networks (all partnered). We found little support for differences in social motives. All network types differed in daily interaction quantity but did not differ in daily relationship quality. The study highlights the heterogeneity of personal networks in middle-aged adults living alone. Possible implications for the social embeddedness and psychological adaptation of people living alone in midlife are discussed.