The average Tamoxifen cash price is about $23.65 for a supply of: Tablet 20 MG 30 pcs. Get our free Tamoxifen coupon and be eligible to receive a discount. You can reduce your Tamoxifen cost by up to 75% with our free Tamoxifen discount card. Bring it to a participating pharmacy near you to save on your prescription medication.Tamoxifen blocks the actions of estrogen, a female hormone. Certain types of breast cancer require estrogen to grow. Tamoxifen is used to treat some types of breast cancer in men and women. Tamoxifen is also used to lower a woman's chance of developing breast cancer if she has a high risk (such as a family history of breast cancer). Tamoxifen may also be used for purposes not listed in this medication guide.