Sleep disturbances are pervasive in patients with multiple sclerosis (MS), with incidence about four times higher compared to the general population. The most frequent primary sleep problems include insomnia, restless leg syndrome, sleep-related movement disorders, and sleep-disordered breathing. This study aims to assess the relationships between sleeping problems and the quality of life (QoL) in MS patients. This cross-sectional study was conducted among 152 MS patients (mean age: 36.27 ± 9.60) between November 2018 and February 2019 at a neurological health center in Wroclaw, Poland. The study was based on a questionnaire that included questions concerning sociodemographic and clinical data in addition to the following standardized questionnaires: Athens Insomnia Scale (AIS), Epworth Sleepiness Scale (ESS), and Multiple Sclerosis International Quality of Life (MusiQoL). The degree of physical disability was evaluated following the Expanded Disability Status Scale (EDSS). Analysis of the research material showed that 66.45% of MS patients had insomnia, and 41.45% presented with daytime sleepiness. The QoL of respondents was assessed as average (50.73). Univariate linear regression model analysis showed the effects of professional status, daytime sleepiness, insomnia, and degree of disability on the QoL of MS patients. Sleep disturbances are widespread in MS patients. The presence of sleep disturbances (insomnia and daytime sleepiness) significantly affects the QoL of MS patients.