U.S. companies said they are tempering the effects of escalating tariffs with China through price increases or changes to their supply chains, but they warn investors that the picture could worsen next year.

Tariffs have slowed U.S. timber and grain exports, raised the cost of imported clothes hangers and heavy-equipment materials, and compressed profit margins for computer chip and tool makers, among other effects, according to an analysis of results and comments from the roughly 75% of S&P 500 companies that have reported...