The loonie was up 0.22 of a cent to 89.51 cents US.
The Institute for Supply Management's manufacturing index came in at 56.6, down from 59 in August and much weaker than the 58 reading that economists had expected.
The reading added to weak manufacturing reports in recent days from China and Europe.
"PMIs (Purchasing Managers Indexes) overseas have disappointed, and the U.S. has joined the parade," said CIBC World Markets chief economist Avery Shenfeld.
He also pointed out that the 56.6 reading for September "is still consistent with solid growth, and perhaps just more in line with reality than the outsized 59 reading registered in August."
The manufacturing data came amid a strong indication of U.S. job creation.
Two days before the release of the U.S. government's employment report, payroll firm ADP said that the American private sector created 213,000 jobs last month, in line with expectations.
Economists are expecting the U.S. Labor Department to report Friday that about 215,000 jobs were added in the private and public sectors during September.
Canadian jobs data for last month won't be released until Oct. 10.
The Canadian currency had a tough September, losing about two U.S. cents to drop to levels most recently seen in late March.
The loonie has come under pressure from a greenback that steadily appreciated amid positive American economic data and speculation about when the U.S. Federal Reserve may start to raise interest rates.
Markets have generally looked for the Fed to raise rates around the middle of 2015, although the U.S. central bank has said its move will depend on economic data rather than a schedule.
The commodity-sensitive Canadian currency has also been pressured by weaker oil and metal prices because of the rising U.S. dollar and weak Chinese data. A stronger U.S. dollar makes it more expensive for holders of other currencies to buy oil and metals which are U.S.-dollar-denominated.
Commodity prices were mixed Wednesday as November crude in New York surrendered early gains to close down 43 cent to US$90.73 a barrel after lower demand and a glut of supply sent oil tumbling five per cent during September to its lowest closing price in almost two years.
December copper gained three cents to US$3.04 a pound after lower demand pushed the metal viewed as an economic barometer down five per cent during September.
Gold for December gained $3.90 to US$1,215.50 after losing almost six per cent last month amid low inflation readings in most parts of the globe.