Malone struck the winner to end the game 23-21 just moments after London Irish winger Paul Sackey looked like he had secured a famous victory at The Rec with a try – but visiting fly-half Barry Everitt failed to convert, leaving the door open for Malone's crowning moment.
Bath's 16th Zurich Premiership victory of the season has all but secured Heineken Cup qualification for the league leaders.
Bath, European Cup champions in 1998, have been absent from the competition for the last two seasons, but are now on the verge of returning to the continent's senior competition.
But the Exiles, again, came so close to upsetting Bath's remarkable swagger.
Indeed, it was the visitors who drew first blood when centre Nils Mordt claimed a dramatic converted try after just three minutes as Bath reacted slowly to a quick Irish throw-in.
Bath finally opened their account in the 18th minute through winger Alex Crockett, who latched onto a chip ahead by fullback Paul Sampson and forced his way over the tryline.
Malone's conversion hit the post, but he made amends moments later by slotting a penalty goal to gift Bath a 8-7 lead.
Everitt and Malone exchanged a further penalty each before the break, to leave the half-time score at 11-10 in the home side's favour.
The kicking duel continued after the break with a penalty apiece, but Malone upped the ante by converting the first of his two drop-goals on the hour mark to give his side a vital four-point advantage.
That was stretched to seven points with his fourth penalty goal, but the Exiles soon silenced the expectant home crowd.
Everitt landed his third penalty goal to narrow the gap before Sackey stepped up to score his try for London Irish in the final minute of regulation time.
But Bath are not league leaders for nothing – the Bath forwards muscled their fly-half within range of their visitors' posts and Malone acknowledged their work by letting fly with the 35-metre winner in the third minute of injury-time.
For Bath:Try: CrockettPens: Malone 4DGs: Malone 2
For London Irish:Tries: Mordt, SackeyCon: EverittPens: Everitt 3