Camden and Islington councils said the move was radical, would cut management costs and could throw open "greater opportunity for innovation and shared services".
The two London councils need to close funding gaps of up to £100m each, said an Islington representative. Closer partnership could save cash and create efficiencies.
"A decision on sharing a chief executive and some directors is due before Christmas. The parks function is quite a way down the line, so it's too early to say it will happen," the representative confirmed.
Parks consultant Sid Sullivan said: "This could have big strategic implications. If both have green-space strategies, will they conflict? And how will a single head of parks bring them together? Will it add complexity with issues of budgeting and priorities?
"And will funders, suppliers and contractors be sophisticated enough to deal with the new complexity? The flip side is that one big bid for money to, say, the Heritage Lottery Fund, could carry more weight than two smaller ones.
"This is good as it raises the prospect of a big, more powerful department with the critical mass to carry more clout. In the past, chief executives said parks weren't big enough. They will be now."
The power-sharing idea came about when John Foster, chief executive of Islington, said he would retire next May. He is said to earn around £210,000.
If both councils agree to the move, his Camden counterpart Moira Gibb would also take the helm at Islington. She is reported to earn around £230,000.
Camden leader Nasim Ali said: "As the scale of the cuts to public services becomes clearer it is right that we examine all options."
Islington leader Catherine West added: "By working together we have a combined purchasing power and more clout to get better value." Camden has an annual budget of £264m and Islington £243m.