Background: Between 40%-60% of nursing home patients with dementia suffer from chronic and acute pain despite increasing their analgesic drug prescription. Aims: Determine the locations and intensity of pain and the association between quality of life (QoL) and four stratified pain–analgesic groups: (1) pain—analgesics treatment; (2) pain—no analgesics; (3) no pain—analgesics treatment; and (4) no pain—no analgesics. Design: Multicenter, multicomponent cluster randomized controlled Communication, Systematic assessment and treatment of pain, Medication review, Occupational therapy, and Safety - an effectiveness (COSMOS) trial. Participants: At baseline, 723 nursing home patients were enrolled; 463 were completely evaluated for the presence of pain and included in the cross-sectional analyses. Methods: Data were collected using the following tests: Cognitive function (Mini-Mental-State Evaluation [MMSE]); Quality of Life in Late stage of Dementia (QUALID); Dementia-Specific QoL (QUALIDEM); Mobilization–Observation–Behavior–Intensity–Dementia Pain Scale (MOBID-2); and number of analgesic drug prescriptions. Analysis of covariance (ANCOVA) was used to compare pain and QoL across pain–analgesics groups. Results: The majority of participants (78%) had moderate-to-severe dementia, were female (74%), and a mean age of 86.7 years. Almost 44% reported clinically significant pain, whereas 69% had ≥2 pain locations, especially in the musculoskeletal system. Some 33.5% of participants had pain receiving analgesics, 10% had pain with no analgesics, and 27% had no pain receiving analgesics. Patients evaluated with clinically significant pain intensity scores had lower QoL (<.001) compared with assessments relying on different pain locations. Conclusion: Untreated musculoskeletal and multi-located pain is still common in nursing home patients with dementia. A significant share without pain receive analgesics. Proper pain assessment and regular re-assessment are prerequisites for the prescribing and deprescribing of analgesics. Pain intensity scores are more significantly connected to QoL. This must be stressed when evaluating pain and QoL.