Head Coach Richard Hill today described the two signatures as crucial and a real statement of intent about where Warriors are going as a club and striving to achieve in the coming years.
Back row giant Senatore, who can play at flanker or Number Eight, is one of the most exciting talents in Argentinean rugby having already won 17 caps for his country.
The abrasive 28-year-old impressed at the 2011 Rugby World Cup before enjoying a spell in the Top 14 in France with Toulon. He last played for Argentina against Ireland at Lansdowne Road in November.
"Leonardo is a fantastic signing for Warriors. Like the vast majority of Argentinean players he is very passionate about his rugby, will give everything, is very dedicated and extremely loyal," said Hill.
"He has good technical ability and is a strong ball carrying back row forward of considerable size. Leonardo is a real athlete who brings vast experience from his international action.
"We have seen him in action for Argentina and in the World Cup. He has been on our radar for the last few years and he has been in fantastic form.
"Leonardo will add experience and quality to our squad and we look forward to him joining."
Inspirational full back Pennell, a home-grown product of the Warriors Academy, has been one of the star performers at Sixways over the last five years and produced some of his very best displays this season.
Worcester born-and-bred, Pennell, who was club captain between 2010 and 2012, is now closing in a century of appearances for Warriors and has already featured on 16 occasions in all competitions this term.
"When I first joined Worcester Warriors I was told that Chris was the future of the club and that very much remains the case today," said Hill.
"His attitude and work ethic is superb and he has really developed himself as a player.
"I always felt he was a potential leader and I made him captain before he suffered two seasons of bad injuries.
"This season he is back to his best and getting better as the season progresses. He has the full confidence of the team around him, is fantastic under the high ball, a good defender and is a strong runner.
"Chris has all the qualities to get even better and so this is a very important re-signing for us."