"Harry is another young player to add to some of the wonderful ones we have already got here," said Leicester boss Ian Holloway.
"We have paid a little bit of money for him.
"He chose not to stay at Chelsea even though they wanted him to sign a new deal. Preston were also in for him.
"He is 6ft 3in and is quick as hell. We see him developing into a very decent centre-half. It may seem to be a bit of a strange one considering where we are in the table, but we are looking at it long term.
"If we get any injuries and we have had a couple of weeks coaching him and working with him then who knows. We might need him between now and the end of the season, but for now he is one to tuck in and leave underneath."
Worley signed for Chelsea from Stockport in the summer of 2005 with a tribunal setting an initial fee of £150,000.