In a series of tweets, the ex-Tory leader revealed he was driving a lorry to the country with goods collected by Oxfordshire food project Chippy Larder.
He said it was filled “with everything from nappies to sanitary products, warm clothes to first-aid kits”.
Mr Cameron and two colleagues from the charity will give the donations to the Red Cross when they reach Poland.
He wrote: “It’s going to be a long drive, but I’ll keep you updated along the way.”
People across the UK have been making donations to charities to help those fleeing Ukraine since the Russian invasion.
Mr Cameron said that Chippy Larder – where he has been volunteering for two years and which provides low-cost food to people in Chipping Norton – began its own collection two weeks ago.
He posted videos on Twitter of the donations, writing: “In the last fortnight we’ve appealed for the things that refugees from Ukraine need as they arrive in Poland. The response has been amazing.”
The former PM added: “The generosity of the community in West Oxfordshire – and of the British people more generally – has been typically phenomenal, stepping up to help our neighbours in their hour of need.”
The Ukrainian ambassador to the UK, Vadym Prystaiko, welcomed the support from the British public earlier on Friday.
But he said “money would be better placed” rather than bulky items.
Mr Prystaiko added: “The message is simple: if you can, give a couple of pounds rather than bring stuff in a bag.”
