“The stray cows and oxen have been a big nuisance in Kathmandu streets. They not only cause accidents, but also make the streets untidy,” said Pawan Giri, spokesman for the Kathmandu Metropolitan Traffic Police.
“We see traffic jams because the drivers who try to avoid the cows often crash into other vehicles.”
He said the captured animals would be detained until their owners paid a fine of approximately US$60 (B1,700) for their release.
Cows are a regular sight in the smog-choked capital and are often seen eating from piles of garbage on the roadside.
Regarded as an incarnation of the Hindu Goddess of prosperity Laxmi, the beasts are sacred in Nepal, where most people are Hindu.
The traffic police say they have rounded up 18 animals since launching the operation and they plan to continue the sweep for several weeks.
Killing a cow is illegal in Nepal, and can carry a prison sentence of up to 12 years.