Shares of Zoetis, whose pipeline includes medicines and vaccines for pets and livestock, were up 2 percent at $56.65 in extended trading.
The company, spun off from Pfizer Inc (PFE.N) in 2013, was valued at $24.85 billion as of Thursday's close, according to Thomson Reuters data.
Both Valeant and Zoetis spokesperson declined to comment.
It was not clear what Zoetis's reaction to the preliminary approach was, if any, or whether it was open to a sale, the Journal reported, citing people familiar with the matter. (on.wsj.com/1fGK2qC)
Zoetis, the world's largest animal-health company, has been cutting costs and said last month it planned to cut up to a quarter of its workforce and exit nearly 40 percent of its manufacturing plants.
The decision came a month after Bill Ackman's Pershing Square, Zoetis's biggest shareholder, and Sachem Head Group seated their second nominee on the company's 11-member board in exchange for not soliciting takeover offers.
Valeant, which lost a bid to buy Botox maker Allergan Inc (AGN.N) in November, is often criticized for a growth plan that is driven by acquisitions and cost-cutting.
Shares of Laval, Quebec-based Valeant closed at C$287.79 on the Toronto Stock Exchange, after rising 73 percent this year; while Zoetis shares closed at $55.38 on the NYSE on Thursday.
Reporting by Rosmi Shaji in Bengaluru; Editing by Joyjeet Das