Background: Although cancer patients experience distressing symptoms and health-related changes in their quality of life, they may report positive emotional states. The lives of informal caregivers of cancer patients may also be affected by the patient's cancer diagnosis; however, they may also find benefits in their experiences. Noticeable changes are reported in personal priorities after an oncologic diagnosis that can lead individuals to restructure their values and the way they perceive life. This study aims to assess happiness/satisfaction with life and positive and negative affect in cancer patients and informal caregivers compared with healthy people in the general population. Methods: A cross-sectional study with participants recruited online in five regions of Brazil through the social network site Facebook® and the application WhatsApp®. Surveys were completed using the SurveyMonkey® platform. A different sample of cancer patients and informal caregivers that was personally interviewed with the same forms was also grouped in the present analysis. Variables with p-values < 0.05 in the univariate analysis were included in linear regression models (stepwise, backward). Results: A total of 2580 participants were included, of whom 2112 were healthy representatives of the general population, 342 were cancer patients, and 126 were informal caregivers of cancer patients. In the multivariate analysis, the cancer patients and informal caregivers were happier than the healthy people in the general population, even after controlling for age, sex, educational level, and income. The patients and caregivers had lower scores for positive affect and higher scores for negative affect. Conclusions: Overall, the conditions related to happiness, satisfaction with life and positive affect are similar for all groups. However, cancer patients and informal caregivers report increased rates of happiness and satisfaction with life compared with theoretically healthy people, although they have lower positive affect scores and higher negative affect scores. It is suggested that cancer patients and caregivers of cancer patients experience more difficulties (suffering) on a daily basis. However, given the increased difficulties, they perceive life differently, reporting that they are happier.