The £7,195 supermini was identified as the car least likely to breakdown or have faults in a survey of over 26,000 customers in the annual car reliability survey.
Only 1.9 per cent of people said they have had problems with the Picanto, the least out of any other model in the survey.
The total score of 98.1 per cent was slightly higher than the second-place Mazda3, which received a score of 97.6 per cent.
Japanese manufacturers took up seven of the top ten places in the survey, including a second Mazda model in the shape of the Mazda2.
Despite the Kia Picanto coming in first place in the reliability study, the Japanese manufacturer is also offering its extended seven year warranty on all vehicles in case anything does go wrong.
In the survey, owners of three year old cars were asked to rate the number of breakdowns, faults and niggles with the vehicle. The rating was worked out by applying a scoring system to each fault, with more inconvenient problems such as breakdowns given more weight.
In contrast to the success of smaller Japanese cars, the least reliable list was dominated by large SUVs and MPVs.
Peter Vicary-Smith, Chief Executive, Which?, says: "Some small cars, particularly Korean and Japanese superminis, run like clockwork. Whereas some bigger cars, which you might expect to be more robust, aren’t all they’re cracked up to be."