Inclusion Criteria:  18 years of age or older Has completed curative-intent treatment (chemo, surgery, RT) for prostate, colon or breast cancer at least three months and not more than 5 years prior to study entry. Note: Ongoing hormonal therapy (i.e., tamoxifen, aromatase inhibitors, casodex), Herceptin and maintenance therapies are allowed. Ability to read and write English Ability to complete questionnaire(s) by themselves or with assistance. Reports trouble falling asleep or staying asleep on at least 3 nights per week (most weeks) for the last 3 months. Own an Android phone version 8 or higher (The latest version of Android is 11.0) or an iPhone running iOS 11 or higher (The latest version of iOS is 14.3.) Ability to provide informed written consent.  Exclusion Criteria:  Inability to read and write English Diagnosis of a sleep disorder other than insomnia (e.g. sleep apnea, restless legs syndrome, narcolepsy) Diagnosis of Insomnia prior to cancer diagnosis Reports physical symptoms that interfere with sleep, such as shortness of breath, pain, hot flashes, frequent urination Major psychiatric or medical condition other than cancer suspected to contribute to their sleep disturbance Evidence of active cancer (i.e. not considered NED) Currently or previously received CBT-I Patients who are night shift workers or subject to other external restrictions on their opportunity to sleep at night.