Oxfordshire Mind experienced a 390% increase in calls in March, but says contact has now dropped off.
More than 1,200 people have sought support from Oxfordshire Mind since lockdown began, with a huge surge in calls to its Information Line initially.
But now, the charity says contact how dropped compared to the peak, leading to concerns people who are struggling are not accessing the support they need.
In an Office for National Statistics study in April 2020, 48% of the British population reported that their mental health had been affected by the COVID-19 crisis.
Experts predict social distancing restrictions will have a long-lasting impact on mental health, especially anxiety and post-traumatic stress disorder.
Dan Knowles, CEO of Oxfordshire Mind, said: "Covid-19 has dramatically highlighted the need for services like ours. The pandemic is changing all our lives and placing huge amounts of stress on our mental health.
"For those already living with mental health difficulties, the self-isolation and social distancing measures put in place, as well as fears about the virus itself, are adding to the pressures of the current situation. Thus, there will be both short and long-term impacts on our mental health."
Oxfordshire Mind has adapted its services to ensure that anyone who needs them can still get support.
There are some face-to-face services available; the Banbury and Oxford Safe Havens are continuing support for people in crisis with reduced 1:1 support and increased phone support.
The charity has increased the number of phone lines for its Information Service and expanded its opening hours by 2.5 hours per week. The team will also undergo continued training to ensure they can respond to people suffering from trauma, bereavement, and anxiety.
The Oxfordshire Mind team has also been providing some residents with pre-paid mobile phones so they can check on their wellbeing regularly.
But like most charities, Oxfordshire Mind's fundraising activities have been significantly impacted by COVID-19, at a time when the need for its services are greater than ever.
So, it's had to launch an appeal for people to donate to keep the charity going, as Dan Knowles explains:
Dan also said a big thank you to all of the Oxfordshire Mind volunteers who help out with the charity every week.
You can donate by clicking here, or by texting MIND 10 to 70470 to donate £10.
Covid-19 is placing huge amounts of stress on our mental health. We've launched an Emergency Appeal to ensure that everyone in Oxfordshire struggling with their mental health has somewhere to turn. If you can, please donate today: https://t.co/jpAkzrn4p1#SomewhereToTurn #OxMind pic.twitter.com/0qwwkCVrlS— Oxfordshire Mind (@OxfordshireMind) June 1, 2020