We studied the concentrations, seasonal distributions, sources, exposures, and health risks of phthalates in indoor and outdoor PM2.5 in Beijing. The results showed that phthalate concentrations during haze periods were significantly higher than during non-haze periods both indoors and outdoors, with higher concentrations for the former, which reached a maximum of 1995.56 ng m–3. Phthalates are mainly derived from the use of indoor plasticized products, the outdoor plastic products industry, and other sources of fuel emissions. Lifelong exposure to fine (2-ethylhexyl) phthalate (DEHP) through inhalation and dermal absorption was calculated, and the results indicated a risk of cancer, with DEHP carcinogenic risk levels of 4.09 × 10–6 and 10.50 × 10–6 for adults and children, respectively. The highest DEHP carcinogenic risk group was 1–2-year-old children, and the risk decreased afterward with age.