How to disable a Field in redux-form?

You can pass the props object:

props : object [optional]: Object with custom props to pass through the Field component into a component provided to component prop. This props will be merged to props provided by Field itself.

// outside your render() method
const renderField = field => (
  <div>
    <input
      {...field.input}
      disabled={field.disabled} // you'll use it here
      type="text"
    />
  </div>
);

// inside your render() method
<Field
  name="myField"
  props={{
    disabled: true, // like this
  }},
  component={renderField}
/>

Apparently, it works if you provide primitive react components rather than functions:

      <Field
        name="firstName"
        component="input"
        type="text"
        disabled={true}
        placeholder="First Name"
      />

So I think the problem in your case is inside the renderField function you have not shown.