Purpose To investigate cancer patients’ knowledge and attitudes regarding fatigue and the potential benefits and acceptability of a brief information booklet. Methods The CARPE DIEM study assessed knowledge and attitudes regarding fatigue in a diverse group of 50 cancer patients before (T0) and about one (T1) and four months (T2) after reading the booklet. At T1, participants additionally rated its usefulness. Results At baseline, 37.5% of respondents did not know the term “fatigue” or what it meant. Those who already knew something about fatigue mainly had obtained their information from booklets, books, or articles (63.3%) and/or the internet (46.7%). Overall, knowledge gaps existed, particularly about potential fatigue treatment options and whether fatigue is an indicator of cancer progression. Furthermore, 56.4% felt poorly informed, and 46.1% reported feeling helpless in the face of fatigue. Lower knowledge at baseline was significantly associated with lower education and older age. At T1 and T2, there were significant improvements in several knowledge questions and attitudes. Patient-reported benefits included getting new information about fatigue (91.1%), awareness of not being alone with their problems (89.7%), taking appropriate actions (72.9%), and encouragement to talk about their fatigue with family/friends (55.3%) or with a health professional (52.7%). Conclusions Specific gaps were identified in the provision of information and education for cancer patients about fatigue. A low-cost intervention asking to read a brief information booklet was associated with improved knowledge. This could be considered as a first step offered as part of a bundle of further efforts to improve knowledge and care of fatigue.