The Arsenal winger suffered a lower leg injury in a tackle with Ecuador's Carlos Gruezo during England's Wednesday night friendly in Miami, putting his 2014 World Cup finals participation potentially in doubt.
The 20-year-old will undergo a scan on Thursday to discover if he will be fit to play in the summer tournament, England's World Cup campaign starting against Italy in Manaus on 14 June.
England manager Roy Hodgson said: "His knee buckled under the the challenge as the player turned into him. He'll have a scan. When we've had the scan, we'll know more."
England were forced to come from a goal behind after eight minutes to lead 2-1 after a close range effort from Wayne Rooney and a fine finish by Rickie Lambert, before the South Americans later leveled through substitute Michael Arroyo's strike.
Oxlade-Chamberlain's injury aside, England's match was also blighted by a red card shown to Raheem Sterling. The Liverpool winger was sent off for a foul on Antonio Valencia and will be suspended for England's final friendly against Honduras on Saturday.
"It would have been nice to win it but certainly there were many positives I can take from it", added Hodgson. "I thought it was a very good game. I was disappointed with the sending off, and the potential injury to one of our players - but as a friendly, a warm-up match for our players, it was good.
"[Ecuador] tested us but we dealt with them very well for long periods, and caused their defence many problems."
This event has finished. There are no odds available.