Jenkins joins after a mixed year in the Top 14 with Toulon while Rees is coming from the Scarlets to boost the Blues after a mixed campaign.
But the 23-year-old Andrews insists there is plenty of room for improvement after a season that saw them crash out in the Pool Stages of the Heineken Cup and a bottom half finish domestically.
"It will be great for the Blues to have the added experience of Gethin and 'Smiler' (Rees) to call on," he told Wales Online.
"We haven't got that many old heads here at the moment, so it's good they are coming."
"We all know what Smiler can do, while Gethin's leadership skills are really good when you're on the field with him," said Andrews.
"He doesn't say a lot but, when he does, you take notice of what he tells you - that's the kind of authority guys like him and Smiler have got.
"I've enjoyed working with him and Smiler in the past. Smiler is a big, strong lad, who brings a lot to the scrum.
"There have been massive changes at the Blues, but we have learnt a lot.
"It's been a good learning season and things are looking promising for the future.
"We lost a lot of players last year and, results-wise, this season hasn't been as we would have liked.
"But a lot of the youngsters are driving on and, hopefully, we will see the fruits of that in the years to come."
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