Oropharyngeal (OP) swabbing is a clinical specimen collection method to diagnose the presence of viral infection in the respiratory tract. During the Covid-19 pandemic, OP swab sampling plays an important role in the disease diagnosis. With its advantages in direct visualization of the swab site and less training requirement on medical professionals, OP swab is massively used for COVID-19 specimen collection in many countries. However, patients may demonstrate less tolerance for the OP swabbing by gagging or closing their mouths, which puts the swab tip in contact with the oral palate or tongue and results in defective sampling. Gagging and other involuntary reactions increase the risk to medical workers who are in direct contact with the patients. To solve these issues, this research presents a novel OP swab assembly which can assist adult patients to collect OP swab specimen by themselves or facilitate adults to collect specimens for their children or disable family members. The OP swab assembly has features to mitigate discomforts in the swab procedures as so to reduce involuntary reactions, minimizing specimen contamination. It also has features to keep the mouth open and constrain the motion of the swab tip in the effective sampling area, furtherly ensuring the high quality of the specimen. Experiments were conducted on a standard adult human skull mannequin by using the presented OP swab assembly. The results demonstrated the feasibility and effectiveness of self-collection for OP swabs using the presented assembly and method.