BACKGROUND: Although remote communication technologies have been widely used to maintain connections with others against interpersonal contact restrictions and exacerbated loneliness during the COVID-19 pandemic, it is unclear whether and what types of remote communication technologies are effective in mitigating loneliness. OBJECTIVE: This study aimed to investigate the association between remote communication and loneliness when face-to-face meetings with others were strongly prohibited and whether this association varied across types of communication tools, age, and gender. METHODS: We used cross-sectional data from the Japan COVID-19 and Society Internet Survey conducted from August to September 2020. From registered panelists of the research agency, 28,000 randomly sampled participants completed the survey on the website. We created 2 study cohorts who stopped meeting with family members living apart and friends during the pandemic. We categorized whether participants had technology-based remote communication (voice calling, text messaging, and video calling) with family and friends. Loneliness was assessed using the 3-item University of California, Los Angeles Loneliness Scale. We used a modified Poisson regression model to investigate the association between loneliness and remote communication with family members living apart or friends. We also conducted subgroup analyses based on age and gender. RESULTS: A total of 4483 participants stopped meeting with family members living apart, and 6783 participants stopped meeting with friends during the COVID-19 pandemic. Remote communication with family members living apart did not show an association with loneliness, whereas remote communication with friends was associated with a low prevalence of loneliness (family: adjusted prevalence ratio [aPR]=0.89, 95% CI 0.74-1.08; P=.24 and friends: aPR=0.82, 95% CI 0.73-0.91; P<.001). From analyses by tools, voice calling was associated with low loneliness (family: aPR=0.88, 95% CI 0.78-0.98; P=.03 and friends: aPR=0.87, 95% CI 0.80-0.95; P=.003). Similarly, text messaging was associated with low loneliness (family: aPR=0.82, 95% CI 0.69-0.97; P=.02 and friends: aPR=0.81, 95% CI 0.73-0.89; P<.001). However, we did not find an association between video calling and loneliness (family: aPR=0.88, 95% CI 0.75-1.02; P=.09 and friends: aPR=0.94, 95% CI 0.85-1.04; P=.25). Text messaging with friends was associated with low loneliness regardless of age, whereas voice calling with family or friends was associated with low loneliness only among participants aged ≥65 years. An association between remote communication with friends and low loneliness was found regardless of the type of remote communication tool among men, whereas it was found only for text messaging with friends among women. CONCLUSIONS: In this cross-sectional study of adults in Japan, remote communication, especially via voice calling and text messaging, was associated with low loneliness. Promoting remote communication may reduce loneliness when face-to-face contact is restricted, which should be the subject of future research.