Journal of Medical Internet Research - International Scientific Journal for Medical Research, Information and Communication on the Internet #Preprint #PeerReviewMe: Warning: This is a unreviewed preprint. Readers are warned that the document has not been peer-reviewed by expert/patient reviewers or an academic editor, may contain misleading claims, and is likely to undergo changes before final publication, if accepted, or may have been rejected/withdrawn. Readers with interest and expertise are encouraged to sign up as peer-reviewer, if the paper is within an open peer-review period. Please cite this preprint only for review purposes or for grant applications and CVs (if you are the author). Background: Social media is rapidly changing how cancer survivors search for and share health information, and can potentially serve as a cost-effective channel to recruit and invite cancer survivors in the community to participate in online intervention programs to improve their nutritional intake. Objective: We aimed to assess the feasibility of using Twitter to recruit cancer survivors for an online survey and assess their willingness to engage with nutrition programs delivered online. Methods: We contacted 301 Twitter accounts of cancer organizations, advocates, and survivors to request assistance with promoting an online survey among cancer survivors using social media and assessed the survey promote rates and yields. We further evaluated the percentage of cancer survivors who indicated willingness to complete online nutrition surveys, donate biospecimens, and engage with nutrition programs delivered online. Results: Over 10 weeks, 113 Twitter account owners and 165 of their followers promoted the survey. A total of 444 cancer survivors provided complete responses. About two-thirds of the survivors indicated that they would be willing to complete online nutrition and lifestyle surveys (67.0%) and participate in nutrition interventions online (66.2%). The percentage of the survivors willing to donate biospecimens were 59.3% for oral swab, 52.1% for urine sample, 37.9% for blood sample, and 35.6% for stool sample. Compared to the 1,550 cancer survivors in the National Health and Nutrition Examination Survey, cancer survivors who responded to the social media survey were younger (53.1 vs. 60.8 years), more likely to be female (93.9 vs. 58.7%) and non-Hispanic Whites (85.4 vs. 64.0%), completed college or graduate school (30.1 vs. 19.9%), and within five years of their initial diagnosis (55.2 vs. 34.1%) (all P <0.0001). Conclusions: Twitter could a feasible approach to reach cancer survivors, offering an avenue for recruitment into nutrition research and online interventions with potentially high yields. Specific efforts are needed to reach survivors who are older, male, and from racial/ethnic minorities and socioeconomically disadvantaged groups when Twitter is used as a recruitment method.