The Greater Birmingham Chambers of Commerce Business Report for the third quarter, in partnership with the University of Birmingham, showed that businesses are moving on from initial concerns about Brexit.
Overall business confidence remained buoyant, with 61% of companies expecting to improve their turnover in the next year.
Paul Faulkner, chief executive of Greater Birmingham Chambers of Commerce, said: "It’s encouraging that the region is feeling optimistic post-Brexit.
"While there was a drop in the proportion of firms reporting an increase in domestic sales - perhaps reflecting the immediate uncertainty following the vote - advance orders are back on trend and confidence remains strong.
"This is a testament to the resilience of Greater Birmingham businesses. However, given some lingering concerns about Brexit, it is not surprising to see that the proportion of firms looking to increase their investment and training budgets dipped this quarter.
"We hope to see greater clarity on the Government’s industrial strategy, investment in infrastructure and investment in the region at the Autumn Statement to further boost confidence amongst British business.
"We know that trading internationally has rarely been more important for the business community. That is why we have just launched the GBCC International Hub, offering comprehensive international trade support."
Figures in the report showed domestic sales for both services and manufacturing firms fell in the immediate aftermath of the referendum.
But manufacturers in particular have bounced back, with 44% recording increased orders, up from 33% in last quarter and the export market continued the same trend. 31% of manufacturers said overseas sales had increased, compared with 29% in Q2 and orders also improved to 38% compared with 32%.
Professor Julian Beer, deputy vice-chancellor at Birmingham City University, said: "Export growth, particularly in the manufacturing sector, appears to be benefiting from Sterling’s depreciation. However, exchange rate volatility is a key concern for the future.
"Overall business sentiment is positive, despite the continued lack of any definition of Brexit, the process of how it will be achieved and when it will be triggered."