Harrington will join the bibs-to-buggies retailer as finance director in the New Year. He replaces Steven Glew, who will leave at the end of the year.
Mothercare chief executive Ben Gordon said: 'Neil's impressive financial, commercial and international expertise in the retail sector will prove invaluable as we move into the next phase of growing the business more aggressively, both in the UK and globally.'
Harrington said: 'I am excited to be joining Mothercare, which is one of the great iconic brands. I look forward to working with the management team to achieve Mothercare's ambitions at what is a key stage in the company's growth.'