Exhibit 99.4

SUBSCRIPTION RIGHTS TO PURCHASE SHARES OF COMMON STOCK

OFFERED PURSUANT TO SUBSCRIPTION RIGHTS

DISTRIBUTED TO SHAREHOLDERS

OF FIRST NATIONAL CORPORATION

May ___, 2012

To Security Dealers, Commercial Banks,

Trust Companies and Other Nominees:

This letter is being distributed to securities dealers, commercial banks, trust companies and other nominees in connection with the rights offering (the “Rights Offering”) by First National Corporation (the “Company”) of Shares (as such term is defined below), pursuant to non-transferable subscription rights (the “Rights”) distributed to all holders of record (the “Recordholders”) of shares of Company common stock, par value $1.25 per share (the “Common Stock”), at 5:00 p.m., Eastern time, on May 4, 2012 (the “Record Date”). The Rights and Common Stock are described in the offering prospectus dated                      , 2012 (the “Prospectus”).

In the Rights Offering, the Company is offering an aggregate of 2,955,649 shares of common stock, as described in the Prospectus.

The Rights will expire, if not exercised prior to 5:00 p.m., Eastern time, on June 25, 2012, unless extended (as it may be extended, the “Expiration Time”).

As described in the accompanying Prospectus, each beneficial owner of Shares registered in your name or the name of your nominee is entitled to one Right for each share of Common Stock owned by such beneficial owner at 5:00 p.m., Eastern time, on the Record Date. Each Right will allow the holder thereof to subscribe for up to one share of common stock (the “Basic Subscription Right”) at the cash price of $4.00 per share (the “Subscription Price”). For example, if a Recordholder owned 100 shares of Common Stock as of 5:00 p.m., Eastern time, on the Record Date, it would receive 100 Rights and would have the right to purchase 100 shares for the Subscription Price.

If a holder purchases all of the shares available to it pursuant to its Basic Subscription Right, it may also exercise an over-subscription privilege (the “Over-