Te Hiku Community Board chairwoman Adele Gardner said she was ''hugely disappointed'' the playground, on South Rd near Te Ahu, had been targeted by thieves.
"This is a very popular destination for local families. The upgrade of the junior play equipment, which was completed only months ago, was undertaken following many requests from residents for equipment for younger tamariki. This theft will directly impact those young children and their caregivers just when the park will be at its busiest."
Kaitaia police are reviewing CCTV footage of the park in a bid to identify the culprits.
Gardner urged anyone with information about the theft, or the whereabouts of the swing seat, to call the council on 0800 920 029 or Kaitaia police on (09) 408 6500.