The reigning champions battled throughout a fiercely contested encounter, but it was Pulse who earned the right to face AO Manchester Thunder in next weekend's Soft & Gentle Grand Final at Co-op Live Arena.
In a repeat of last season's Grand Final, the two sides were inseparable for much of the contest, with only two goals separating them heading into the final quarter.
Lightning made the brighter start from long range, capitalising on the Amex Super Shot period to keep pace with the hosts. Samantha Wallace-Joseph was clinical under the post, converting two Super Shots alongside nine standard goals in the opening quarter, while Berri Neil also landed from distance as the scores remained level at 16-16 after the opening 15 minutes.
The second quarter continued in similar fashion, with neither side able to establish a significant advantage. London Pulse edged ahead through the work of Gracie Smith in centre, whose distribution helped drive the home side's attacking momentum. Despite Lightning continuing to find success during the Super Shot period, Pulse carried a narrow 30-29 lead into half-time.
The contest remained finely balanced after the interval. Sophie Kelly and Liv Tchine combined effectively in attack for Pulse as the hosts gradually extended their advantage. Yet Lightning remained firmly in touch throughout the third quarter, limiting the damage to just a single goal and trailing 44-42 heading into the final period.
The decisive moment arrived early in the fourth quarter as Pulse finally created breathing space. A strong opening five minutes saw the hosts stretch their lead to five goals, forcing a tactical timeout from Lightning Head Coach Vic Burgess.
A reshuffle followed, with Celena Appleby-Prince introduced at wing defence as Lightning searched for a route back into the contest. However, Pulse's defensive unit, led by Funmi Fadoju and Halimat Adio, stood firm during a crucial spell of the game.
Wallace-Joseph continued to threaten during the closing stages with her long-range shooting keeping Lightning within striking distance, but Pulse responded each time. Kelly delivered an influential all-court performance, finishing with 22 goals, three Amex Super Shots and two interceptions from goal attack, helping guide her side over the line.
Despite the disappointment of defeat, Lightning can reflect on another outstanding campaign that saw them reach the post-season for a fifth successive year. Sunday's result brings to an end the club's run of four consecutive Grand Final appearances, while London Pulse advance with the opportunity to defend their title next weekend.