The invention relates to olefin oligomerization methods and methods for reducing/inhibiting fouling in olefin oligomerization reactions comprising: contacting, in an oligomerization reactor (e.g., under oligomerization conditions), an alpha-olefin feed, a catalyst having an olefin selectivity of at least 90 mol % to a desired oligomerization product, a polymer anti-foulant, and optionally a diluent; selectively producing an effluent comprising the desired oligomerization product, unreacted olefin, and alpha-olefin-based polymer byproduct that causes fouling. The amount of polymer anti-foulant can be chosen to limit fouling to ≦20 g/kg desired oligomerization product, to remediate ≧3 grams fouled polymer/kg desired oligomerization product, and/or to reduce/inhibit polymer fouling by ≧10% over a selective oligomerization with substantially no added polymer anti-foulant. Advantageously, desired oligomerization product so obtained can also be polymerized/copolymerized with an alpha-olefin such as ethylene.