Importance: In the absence of a vaccine and therapeutic agent, personal hygiene and physical distancing are essential measures to contain the coronavirus disease 2019 pandemic. Objective: To determine whether a social media campaign, targeted at the gaps in behavior on personal hygiene and physical distancing and distributed nationwide via digital news media, may be an effective method to improve behavior and help to inhibit person-to-person transmission of severe acute respiratory syndrome coronavirus 2. Design, Setting, and Participants: This survey study was designed to uncover self-reported gaps in behavior regarding personal hygiene and physical distancing in the Netherlands. A diagnostic survey was distributed by a large national newspaper (De Telegraaf) and a popular social influencer (Govert Sweep) on March 17, 2020, and was completed by 16 072 participants. Analysis of these outcomes showed that coughing and sneezing in the elbow was done well, but that handwashing, face touching, and physical distancing showed serious gaps compared with advised behavior. This diagnostic information was used to design infographics and a video targeted at repairing these gaps in behavior. The video and infographics were distributed on a national level on March 21, 2020, followed by a postcampaign survey to measure the results on March 24, 2020. Data analysis was performed from March to April 2020. Exposure: Exposed participants were those who viewed the infographics and/or video. Main Outcomes and Measures: Improvement on the extent of handwashing in all areas, handwashing duration of 20 seconds or longer, awareness on face touching, and physical distancing were measured according to responses on the postcampaign survey. Results: A total of 17 189 participants (mean [SD] age, 47.61 [13.57] years; 9100 women [52.9%]) responded to the postcampaign survey. The news article in De Telegraaf was read more than 2 million times, and the influencer video was watched more than 80 000 times. Cross-sectional analysis of the ...