Kadima had wanted to list Mr Sharon as a candidate symbolically, despite his being in a coma in hospital, but could not do so, party spokeswoman, Maya Jacobs said.
"He could not sign the form for joining Kadima, that is why he didn't get a spot," she said.
It will be the first election in three decades in which Mr Sharon, 77, has not run. Mr Sharon was incapacitated by a stroke on January 4.
"All our hearts are with him," Israel's interim Prime Minister, Ehud Olmert, who has assumed Mr Sharon's duties, told a party rally in Jerusalem, kicking off the campaign for the March 28 election that Kadima is forecast by opinion polls to win.
He vowed to fulfil the goals set out by Mr Sharon, alluding to last year's withdrawal from the Gaza Strip, a popular move which Mr Sharon sought to capitalise on when he quit the rightist Likud party in November to found Kadima.
Mr Olmert said he would forge ahead with efforts to resolve Israel's conflict with the Palestinians, with a goal to "shape the permanent borders of the state of Israel as a country with a clear and solid Jewish majority".
Alluding to the electoral victory of Hamas in the January 25 Palestinian parliamentary poll he said "We are not sent into a panic by external threats nor the events of recent days."
Israel has said it would refuse to talk with a Palestinian government that included Hamas, a group committed to the destruction of Israel.
Poll results
Support for the Kadima Party has increased according to the first poll taken since Islamic militants swept the Palestinian election.
But backing for further Israeli withdrawals from occupied territory has weakened substantially following the Hamas victory in last week's Palestinian parliamentary election.
The poll shows Kadima, taking 42 of the Israeli parliament's 120 seats as opposed to 41 in the previous survey.
Likud, which takes a hard line against the Palestinians, added three seats with a total of 16.