Is nolvadex (tamoxifen) a controlled substance?

No: Its generic name is tamoxifen. It acts as a selective agonist/antagonist to estrogen receptors. You need a prescription to get it but it is not a controlled substance.

No: Tamoxifen, the chemical name, is not a controlled substance under the drug enforcement agency - it is considered class 6, (class 1 are "forbidden" - heroin, marijuana), class 2 are very abusable (morphine, oxycodone etc.), class 3- less abusable (hydrocodone, suboxone), class 4 - even less abusable (benzos, Codeine with tylenol). However, it is a drug which should be rx'd by experts, with toxicity.