He claimed First Minister Carwyn Jones was saying "I told you so" while Plaid Cymru was using the poll's outcome as an "excuse" to call for independence.
Labour and Plaid had a "little Britain mentality" when a "globally facing Britain" was needed, Mr Davies wrote.
He made the comments in an article for The Times newspaper's website.
On Thursday, Welsh Government economic advisor Kevin Gardiner said some people were "perhaps unduly pessimistic" after the vote to leave the EU.
Within hours of the Brexit result being announced on June 24, Mr Jones said he feared it would cost Wales jobs.
In his article, to be published on Friday, Mr Davies said the first minister had been "particularly vociferous in his doom-laden economic forecasting, and in denigrating those who chose to leave".
"He has closed the doors on cross-party negotiation and now, having lost his nerve, seems unable to negotiate a deal for Wales, resorting instead to finger-wagging and pronouncements of 'I told you so'," Mr Davies wrote.
Plaid Cymru's call for independence "betrays how out of kilter they are with the needs of Welsh communities", he added.
"The prophets of doom and the independence mongers alike are wrong to take such a warped view of referendum result."
Mr Davies urged his political opponents to "lift their eyes to the sky and consider the limitless potential that now lies ahead of us and to embrace the outcome".
He added: "Instead they seem intent on clinging to a little Britain mentality. A globally facing Britain is what is now needed."
"Prophets of doom" and "independence mongers" are taking a "warped view" of the Brexit vote, Welsh Conservative leader Andrew RT Davies has said.