On 5 May, the 42nd (East Lancashire) Division was dispatched from Egypt. Believing Anzac to be secure, Hamilton moved the Australian 2nd Infantry Brigade and the New Zealand Infantry Brigade, along with 20 Australian field guns, to the Helles front as reserves for the Second Battle of Krithia. Involving a force of 20,000 men, it was the first general attack at Helles and was planned for daylight. French troops were to capture Kereves Dere and the British, Australians and New Zealanders were assigned Krithia and Achi Baba. After 30 minutes of artillery preparation, the assault began at mid-morning on 6 May. The British and French advanced along the Gully, Fir Tree, Krithia and Kereves spurs which were separated by deep gullies, fortified by the Ottomans. As the attackers advanced, they became separated when trying to outflank Ottoman strong points and found themselves in unfamiliar terrain. Under artillery and then machine-gun fire from Ottoman outposts that had not been spotted by British aerial reconnaissance, the attack was stopped; next day, reinforcements resumed the advance.

The attack continued on 7 May and four battalions of New Zealanders attacked up Krithia Spur on 8 May; with the 29th Division the attackers managed to reach a position just south of the village. Late in the afternoon, the Australian 2nd Brigade advanced quickly over open ground to the British front line. Amidst small arms and artillery-fire, the brigade charged towards Krithia and gained 600 m (660 yd), about 400 m (440 yd) short of the objective, with 1,000 casualties. Near Fir Tree Spur, the New Zealanders managed to get forward and link up with the Australians, although the British were held up and the French were exhausted, despite having occupied a point overlooking their objective. The attack was suspended and the Allies dug in, having failed to take Krithia or Achi Baba.

About one-third of the Allied soldiers who fought in the battle became casualties. General Hamilton could ill-afford such losses as they made it difficult enough to hold the little ground he had, let alone continue to capture more. The poor planning of the battle extended to the medical provisions for the wounded which were woeful. The few stretcher bearers that were available often had to carry their burdens all the way to the beach as there was no intermediate collecting station with wagon transport. The hospital ship arrangements were also inadequate so that once the wounded were taken off the beach they would have trouble finding a ship prepared to take them on board. With the failure of the second battle, Hamilton made a request to the British Secretary of State for War, Lord Kitchener, for an additional four divisions. He was promised the British 52nd (Lowland) Division but would not receive any more until August.