Patient-doctor communication is a fundamental component of patients' care. Withholding important information to the doctor can negatively affect the patients' health and patient-doctor communication.Aim: This study aimed to explore the fundamental types of information that patients hide from doctors, eg, the use of medication, health-related lifestyle, or disagreement with the doctor's plan. In addition, this study examines the prevalence and reasons for this nondisclosure and factors associated with it. Methodology: An online survey was conducted using a self-designed questionnaire, which was distributed to social media, targeting the residents of Saudi Arabia from February 1, 2021 to February 28, 2021. Respondents under 18 years of age and those who provided incomplete/incorrect data were excluded from the study. Types of nondisclosed information and their reasons were evaluated. Results: A total of 2725 participants completed the questionnaire, and 1392 (51.1%) were males. About 43.2% of the participants were 18-29 years. Most (82%) responded "yes" to the question "Have you ever withheld any information from your doctor?" Nondisclosed information commonly involved disagreements with the recommendation (44.7%), not taking prescription medication as instructed (40.6%), and not understanding the instructions (37.4%). The most frequent reasons (68.7%) for nondisclosure were that the participants wanted to undergo further tests, did not like the doctor's attitude (48.7%) and felt it did not matter to the doctor (43.2%). Those under 40 were more apt to withhold information (70.4%) than older participants (29.6%) p value = 0.0034. Other factors like gender, education level, and marital status were not associated with nondisclosure. Conclusion:The prevalence of nondisclosure to doctors is high. Effective communication skills and sound doctor-patient relationships may reduce this risk and improve the care delivered to the patients.