City drew a blank at home for the first time this season, as Cardiff strengthened their lead at the top of the npower Championship with a 1-0 win at King Power Stadium.
Craig Bellamy's expert finish halfway through the first half settled a close encounter in the Welsh side's favour, as Nigel Pearson's Foxes were left to rue a host of first-half chances that went begging.
Pearson's men bossed the game's opening quarter, carving out chance after chance, but were ultimately frustrated by in-form Bluebirds 'keeper David Marshall.
And once Bellamy had given Malky Mackay's men a 25th-minute lead, converting Kim Bo-Kyung's cross from the right, the visitors had the slender lead they needed to galvanise their defences.
City continued to press for an equaliser in the second period, but ultimately came up short against the side setting the pace in the division, and head to second-placed Huil City on Boxing Day 10 points behind them.
Both sides came into the game on the back of defeats, but it was the hosts, full of energy and aggression, that made the faster start.
Leading scorer David Nugent was among the first to be frustrated by the reflexes of Marshall, who also reacted well to push out a Wes Morgan header from Anthony Knockaert's corner.
Cardiff failed to clear the danger, allowing Leicester to reload the attack, which ended with a fierce Andy King drive coming back off the post and an offside Jamie Vardy rattling the crossbar.
Knockaert drew awkward saves from Marshall with two strikes from distance, but they were either side of Bellamy's decisive contribution - a controlled first-time shot speared into the bottom corner after Kim's productive run to the byline.
It took the wind out of City sails considerably, although Vardy hit the woodwork again in first-half stoppage time, glancing a Paul Konchesky cross onto the top of the crossbar.
Their efforts to mount momentum after the break were hit by Vardy's withdrawal early in the second period and, as frustrations grew, so did Cardiff's belief.
Inspired by the outstanding central defensive combination of Mark Hudson and Ben Turner, the Welsh side dealt with most things City threw at them, while threatening ominously on the counter-attack.
An outstanding King clearance prevented Aron Gunnarsson tapping in from Bellamy's centre and Ritchie De Laet slid in to deny substitute Rudy Gestede.
But for all of the hosts' excellent recovery work in defence, they were unable to mount sufficient pressure to make it a nervous finale for the leaders.
Their luck on the day was summed up towards the end, when substitute Ben Marshall's corner was met by the head of Nugent, but Craig Conway headed off the line with Marshall beaten.
A frustrating afternoon for the Foxes, but the festive period gets no easier with a trip to second-placed Hull on Boxing Day looming.
City (4-4-2): Schmeichel; De Laet, Morgan (c), Whitbread, Konchesky; Knockaert (Marshall f2), King, Drinkwater, Dyer (Lingard 62); Nugent, Vardy (Waghorn 51).
Unused subs: Logan, James, Moore, Futacs.
Cardiff (4-4-2): Marshall; Connolly, Hudson (c), Turner, Taylor; Conway, Mutch (Gunnarsson 76), Whittingham, Kim (Cowie 51); Helguson (Gestede 55), Bellamy.
Unused subs: Lewis, McNaughton, Noone, Mason.
Goals: Bellamy 25
Booked: Connolly, Turner, Whittingham
Attendance: 25,055 (2,127 away)
Referee: Graham Salisbury (Lancashire)