Background: To evaluate how a national policy of testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) regardless of symptoms was implemented during outbreaks in Dutch nursing homes in the second wave of the pandemic and to explore barriers and facilitators to serial testing. Methods: We conducted a mixed-method study of nursing homes in the Netherlands with a SARS-CoV-2 outbreak after 15 September 2020. Direct care staff and management from 355 healthcare organizations were invited to participate in a digital survey. A total of 74 out of 355 (20.9%) healthcare organizations participated and provided information about 117 nursing homes. We conducted 26 in-depth interviews on the outbreak and the testing strategy used. We also conducted four focus group meetings involving managers, physicians, nurses, and certified health assistants. Recordings were transcribed and data were thematically analyzed. Results: One hundred and four nursing homes (89%) tested residents regardless of their symptoms during the outbreak, and 85 nursing homes (73%) tested the staff regardless of their symptoms. However, interviews showed testing was sometimes implemented during later stages of the outbreak and was not always followed up with serial testing. Barriers to serial testing regardless of symptoms were lack of knowledge of local leaders with decisional making authority, lack of a cohort ward or skilled staff, and insufficient collaboration with laboratories or local public health services. Important facilitators to serial testing were staff willingness to undergo testing and the availability of polymerase chain reaction (PCR) tests. Conclusions: Serial testing regardless of symptoms was only partially implemented. The response rate of 21% of nursing home organizations gives a risk of selection bias. Barriers to testing need to be addressed. A national implementation policy that promotes collaboration between public health services and nursing homes and educates management and care staff is necessary.