Background Breast cancer is one of the most prevalent types of cancer in the female population. The cultural diversity, religious beliefs, myths, and misinformation regarding the disease contribute to diagnostic delays and enhanced burden on the healthcare system. This study aimed to ascertain the extent of knowledge and prevalence of erroneous beliefs and misconceptions regarding breast cancer among Pakistani women belonging to diverse socioeconomic and educational backgrounds. Methodology This cross-sectional study was performed in a tertiary care hospital in Karachi, Pakistan. A total of 350 women were enrolled in the study as a representative female population, and 300 participants were included who met the inclusion criteria. Participants were conveniently interviewed using a pre-piloted questionnaire designed to assess the prevalent myths and misconceptions about breast cancer. The data were analyzed by SPSS version 23 (IBM Corp., Armonk, NY, USA) using descriptive statistics. Results The study findings point to a significant prevalence of erroneous beliefs and a lack of accurate information on breast cancer. The mean age of the participants was 20.8 ± 10.4 years. The majority of the participants belonged to a middle socioeconomic status (70%) and were undergraduates (61.4%). The participants' friends and family members were the most frequent sources of information regarding breast cancer. The most common myth was "breast-feeding offers immunity to breast cancer completely" (76.6%), followed by "breast cancer spreads after biopsy" (63.8%). Participants also believed that breast tissue biopsy can lead to the spread of cancer (63.4%) and that faith healers and alternative medicine can cure breast cancer (47.5%). One-third (33.3%) of the participants considered all lumps to be breast cancer; however, approximately half (41.6%) of the participants thought that only painful lumps were associated with breast cancer. A significant number of participants believed breast cancer to be a result of God's curse (31.4%) or evil eye (38.7%). Conclusions The findings suggest a critical need for community-based breast health education initiatives that take into account Pakistani women's distinctive cultural and societal attitudes and work to dispel common misconceptions about the condition.