He was speaking at a UN summit on counter-terrorism, where he urged donors to do more to support military and developmental efforts to stop violent extremism.
Recently the Sahel has suffered an increase in jihadist and ethnic violence, and sometimes a combination of both.
The G5 Sahel, a multinational counter-terrorism force in the region, has been largely underfunded and failed to counter the threat from groups linked to al-Qaeda and the Islamic State group.
Mr Guterres thinks there needs to be a change in attitude towards the force and its job, and he wants the international community to care more.
“I think we need on one hand to make the mandate stronger, we need to make the funding more predictable but I think probably the G5 is no longer enough," he told the BBC.
"I think we need to look into a broader regional context. We need to engage with the countries of West Africa with stronger support from the international community,“ he said.
This week the European Union pledged an additional $150m (£120m) to the G5 Sahel force, but many other donors have failed to deliver promised funds. And two years after it was formed, the force has barely got off the ground.