Karol Nawrocki said in a video posted on X that the bill, if signed into law, could have worsened the treatment of animals instead of improving it.
He argued that while the bill had sought to improve animal protection, some provisions risked producing "the opposite effect."
President OKs plan to ban fur farming
At the same time, the president said he had signed a separate bill banning fur farming in Poland.
The measure includes compensation for farmers who shut down their operations early, support and severance for workers, and an eight-year transition period.
"Responsibility for animals is an important measure of our social sensitivity, but it cannot come at the expense of the Polish countryside or the interests of Polish farmers," Nawrocki said.
"Reconciling these concerns requires prudence," he added.
Nawrocki said future decisions must balance animal welfare with the interests of farmers and the country’s food security.
He also announced a presidential bill "to protect agricultural production," which he said would be consulted with farmers before being submitted to parliament.
Government officials criticised Nawrocki's veto, calling it the latest in a series of moves by the conservative president to block policies advanced by Prime Minister Donald Tusk's centrist Cabinet.
"President Nawrocki has vetoed a law that would have banned the keeping of dogs on chains. This veto hurts most those who cannot defend themselves," government spokesman Adam Szłapka wrote on social media.
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Source: IAR, PAP, polskieradio24.pl