The charity will run the ad until June in an attempt to secure financial support and raise awareness for its work, which will involve it providing more than 1.8m free treatments to animals this year.
The ad continues the charity's theme of giving something back to sick and injured pets that need donors' help. It features the Eva Cassidy song 'True Colours' and a voiceover by Stephen Tompkinson.
The ad will direct donors to the phone and from April 30, a specially designed microsite,
Jon Bodenham, director of marketing and income generation at PDSA, said: "Once again WPN have created an emotive ad with clear stand out and a compelling call to action."
Airtime planning and buying is handled by Mike Colling & Co and the ad will air on Channel 4 and selected satellite stations.
Earlier this year PDSA chose WPN to handle a shift in activity towards digital marketing.