Do I still get my old vacation pay if I keep working after the sale?

Yes, in the sense that matters most. Under the Employment Standards Act, 2000, when a business is sold and the new owner keeps you on, your employment is treated as continuous rather than as a fresh start — your prior years of service with the seller count toward your vacation entitlement going forward, rather than resetting to zero.

What can get confusing is the vacation pay you'd already earned but hadn't taken or been paid out before the sale closed. As between the seller and the buyer, who is actually responsible for paying out that accrued, unused vacation is something the purchase agreement between them typically deals with directly — it might be paid out by the seller before closing, or assumed by the buyer as a liability it's taking on. Either way, from your side as the employee, that vacation pay is owed to you; you shouldn't simply lose it because ownership changed hands.

If you're not sure whether your accrued vacation was paid out or carried forward, ask your new employer directly and in writing, and keep your own pay stubs and vacation records from before the sale in case a dispute ever comes up about what you're owed.