The present invention provides: an anti-fogging composition which exhibits excellent anti-fogging properties, long-term sustainability of anti-fogging performance, and transparency, and suppresses adhesion between films when coated on a film； an anti-fogging layer formed from the anti-fogging composition； and an anti-fogging film on which the anti-fogging layer is formed. The present invention provides an anti-fogging composition which contains necklace-shaped colloidal silica in which the primary particles of the colloidal silica are bonded in a ring shape, and chain-shaped colloidal silica in which the primary particles of the colloidal silica are bonded in a chain shape, and is characterized in that given that the sum of the solid-content mass of the necklace-shaped colloidal silica and the solid-content mass of the chain-shaped colloidal silica is 100 mass%, the solid-content mass of the necklace-shaped colloidal silica is 5-85 mass% and the solid-content mass of the chain-shaped colloidal silica is 15-95 mass%.【課題】防曇性及び防曇性能の長期持続性、並びに透明性に優れ、フィルムに塗布した際にフィルム同士の密着が抑制される防曇性組成物、当該防曇性組成物により形成された防曇層、及び、当該防曇層が形成された防曇性フィルムを提供する。【解決手段】コロイダルシリカの一次粒子が環状に結合したネックレス状コロイダルシリカと、コロイダルシリカの一次粒子が鎖状に結合した鎖状コロイダルシリカとを含有し、 前記ネックレス状コロイダルシリカの固形分質量と、前記鎖状コロイダルシリカの固形分質量との合計を１００質量％として、前記ネックレス状コロイダルシリカの固形分質量が５～８５質量％であり、前記鎖状コロイダルシリカの固形分質量が１５～９５質量％である、ことを特徴とする防曇性組成物。【選択図】なし
